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Walker V. The Intricacies of Renal Phosphate Reabsorption-An Overview. Int J Mol Sci 2024; 25:4684. [PMID: 38731904 PMCID: PMC11083860 DOI: 10.3390/ijms25094684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/17/2024] [Accepted: 04/19/2024] [Indexed: 05/13/2024] Open
Abstract
To maintain an optimal body content of phosphorus throughout postnatal life, variable phosphate absorption from food must be finely matched with urinary excretion. This amazing feat is accomplished through synchronised phosphate transport by myriads of ciliated cells lining the renal proximal tubules. These respond in real time to changes in phosphate and composition of the renal filtrate and to hormonal instructions. How they do this has stimulated decades of research. New analytical techniques, coupled with incredible advances in computer technology, have opened new avenues for investigation at a sub-cellular level. There has been a surge of research into different aspects of the process. These have verified long-held beliefs and are also dramatically extending our vision of the intense, integrated, intracellular activity which mediates phosphate absorption. Already, some have indicated new approaches for pharmacological intervention to regulate phosphate in common conditions, including chronic renal failure and osteoporosis, as well as rare inherited biochemical disorders. It is a rapidly evolving field. The aim here is to provide an overview of our current knowledge, to show where it is leading, and where there are uncertainties. Hopefully, this will raise questions and stimulate new ideas for further research.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton General Hospital, Southampton S016 6YD, UK
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2
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Abstract
Calcium kidney stones are common worldwide. Most are idiopathic and composed of calcium oxalate. Calcium phosphate is present in around 80% and may initiate stone formation. Stone production is multifactorial with a polygenic genetic contribution. Phosphaturia is found frequently among stone formers but until recently received scant attention. This review examines possible mechanisms for the phosphaturia and its relevance to stone formation from a wide angle. There is a striking lack of clinical data. Phosphaturia is associated, but not correlated, with hypercalciuria, increased 1,25 dihydroxy-vitamin D [1,25 (OH)2D], and sometimes evidence of disturbances in proximal renal tubular function. Phosphate reabsorption in the proximal renal tubules requires tightly regulated interaction of many proteins. Paracellular flow through intercellular tight junctions is the major route of phosphate absorption from the intestine and can be reduced therapeutically in hyperphosphatemic patients. In monogenic defects stones develop when phosphaturia is associated with hypercalciuria, generally explained by increased 1,25 (OH)2D production in response to hypophosphatemia. Calcification does not occur in disorders with increased FGF23 when phosphaturia occurs in isolation and 1,25 (OH)2D is suppressed. Candidate gene studies have identified mutations in the phosphate transporters, but in few individuals. One genome-wide study identified a polymorphism of the phosphate transporter gene SLC34A4 associated with stones. Others did not find mutations obviously linked to phosphate reabsorption. Future genetic studies should have a wide trawl and should focus initially on groups of patients with clearly defined phenotypes. The global data should be pooled.
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Affiliation(s)
- Valerie Walker
- Department of Clinical Biochemistry, University Hospital Southampton NHS Foundation Trust, Southampton, United Kingdom.
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3
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Sutera FM, Giannola LI, Murgia D, De Caro V. Assessment of in vivo organ-uptake and in silico prediction of CYP mediated metabolism of DA-Phen, a new dopaminergic agent. Comput Biol Chem 2017; 71:63-69. [PMID: 28985485 DOI: 10.1016/j.compbiolchem.2017.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 08/01/2017] [Accepted: 09/25/2017] [Indexed: 11/27/2022]
Abstract
The drug development process strives to predict metabolic fate of a drug candidate, together with its uptake in major organs, whether they act as target, deposit or metabolism sites, to the aim of establish a relationship between the pharmacodynamics and the pharmacokinetics and highlight the potential toxicity of the drug candidate. The present study was aimed at evaluating the in vivo uptake of 2-Amino-N-[2-(3,4-dihydroxy-phenyl)-ethyl]-3-phenyl-propionamide (DA-Phen) - a new dopaminergic neurotransmission modulator, in target and non-target organs of animal subjects and integrating these data with SMARTCyp results, an in silico method that predicts the sites of cytochrome P450-mediated metabolism of drug-like molecules. Wistar rats, subjected to two different behavioural studies in which DA-Phen was intraperitoneally administrated at a dose equal to 0.03mmol/kg, were sacrificed after the experimental protocols and their major organs were analysed to quantify the drug uptake. The data obtained were integrated with in silico prediction of potential metabolites of DA-Phen using the SmartCYP predictive tool. DA-Phen reached quantitatively the Central Nervous System and the results showed that the amide bond of the DA-Phen is scarcely hydrolysed as it was found intact in analyzed organs. As a consequence, it is possible to assume that DA-Phen acts as dopaminergic modulator per se and not as a Dopamine prodrug, thus avoiding peripheral release and toxic side effects due to the endogenous neurotransmitter. Furthermore the identification of potential metabolites related to biotransformation of the drug candidate leads to a more careful evaluation of the appropriate route of administration for future intended therapeutic aims and potential translation into clinical studies.
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Affiliation(s)
- Flavia Maria Sutera
- SiSaf Ltd, Innovation Centre, Northern Ireland Science Park, Queen's Island, Belfast, BT3 9DT, UK
| | - Libero Italo Giannola
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, Via Archirafi 32, 90123, Palermo, Italy
| | - Denise Murgia
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, Via Archirafi 32, 90123, Palermo, Italy
| | - Viviana De Caro
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università di Palermo, Via Archirafi 32, 90123, Palermo, Italy.
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Kajiwara M, Ban T, Matsubara K, Nakanishi Y, Masuda S. Urinary Dopamine as a Potential Index of the Transport Activity of Multidrug and Toxin Extrusion in the Kidney. Int J Mol Sci 2016; 17:ijms17081228. [PMID: 27483254 PMCID: PMC5000626 DOI: 10.3390/ijms17081228] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/21/2016] [Accepted: 07/25/2016] [Indexed: 01/11/2023] Open
Abstract
Dopamine is a cationic natriuretic catecholamine synthesized in proximal tubular cells (PTCs) of the kidney before secretion into the lumen, a key site of its action. However, the molecular mechanisms underlying dopamine secretion into the lumen remain unclear. Multidrug and toxin extrusion (MATE) is a H+/organic cation antiporter that is highly expressed in the brush border membrane of PTCs and mediates the efflux of organic cations, including metformin and cisplatin, from the epithelial cells into the urine. Therefore, we hypothesized that MATE mediates dopamine secretion, a cationic catecholamine, into the tubule lumen, thereby regulating natriuresis. Here, we show that [3H]dopamine uptake in human (h) MATE1-, hMATE-2K- and mouse (m) MATE-expressing cells exhibited saturable kinetics. Fluid retention and decreased urinary excretion of dopamine and Na+ were observed in Mate1-knockout mice compared to that in wild-type mice. Imatinib, a MATE inhibitor, inhibited [3H]dopamine uptake by hMATE1-, hMATE2-K- and mMATE1-expressing cells in a concentration-dependent manner. At clinically-relevant concentrations, imatinib inhibited [3H]dopamine uptake by hMATE1- and hMATE2-K-expressing cells. The urinary excretion of dopamine and Na+ decreased and fluid retention occurred in imatinib-treated mice. In conclusion, MATE transporters secrete renally-synthesized dopamine, and therefore, urinary dopamine has the potential to be an index of the MATE transporter activity.
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Affiliation(s)
- Moto Kajiwara
- Department of Pharmacy, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Tsuyoshi Ban
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
| | - Kazuo Matsubara
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, 54 Kawaharacho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
| | - Yoichi Nakanishi
- Research Institute for Diseases of the Chest, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
| | - Satohiro Masuda
- Department of Pharmacy, Kyushu University Hospital, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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Bataille A, Payen D, Villiers S, Chazalet JJ, Jacob L. Evolution of Hemodynamic and Functional Human Kidney Graft Dose Response to Dopamine Using an Implantable Doppler Device. EXP CLIN TRANSPLANT 2016; 14:176-83. [PMID: 26767705 DOI: 10.6002/ect.2015.0181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVES The relation between dopamine infusion and renal hemodynamics and function has not been studied in renal allografts during early recovery. We analyzed the dose response of dopamine infusion on renal blood flow and function in human kidney transplant recipients at reperfusion and during early graft recovery. MATERIALS AND METHODS Phasic and mean renal blood flow was measured by the pulsed Doppler technique using implantable Doppler microprobes in contact with the graft artery. Systemic and renal parameters were recorded on dopamine infusion (0, 3, 5, and 10 μg·kg⁻¹·min⁻¹) immediately after transplant (day 0) in 13 patients and at day 6 in 7/13 patients with early graft recovery. Results are expressed as median and interquartile range between the 25th and 75th percentiles. RESULTS RESULTS At day 0, 3 μg·kg⁻¹·min⁻¹) dopamine did not increase mean renal blood flow over baseline (580 mL/min [219-663 mL/min] vs 542 mL/min [207-686 mL/min]; P = .84). There was an absence of effect with higher dopamine doses, whereas cardiac output, heart rate, and systolic and mean arterial pressure were significantly increased. Urinary sodium excretion, creatinine clearance, and urine output increased dose dependently, with a positive correlation between the increase in urine output and mean arterial pressure (r = 0.48, P < .001). At day 6, 3 μg·kg⁻¹·min⁻¹ dopamine increased mean renal blood flow over baseline (318 mL/min [234-897 mL/min] vs 191 mL/min [173-706 mL/min]; P = .016), with no further increase at higher doses. CONCLUSIONS Immediately after transplant, kidney grafts with ischemic-reperfusion injury are fully dilated and do not respond to dopamine. The specific renal effects observed are due to systemic hemodynamic status. Vascular responsiveness to a "renal dopamine dose" returns on graft recovery.
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Affiliation(s)
- Aurélien Bataille
- From the Department of Anesthesia and Intensive Care, Groupe Hospitalier Universitaire Saint-Louis-Lariboisière-Fernand-Widal, Assistance Publique-Hôpitaux de Paris, 75010, France
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6
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Heath F, Newman A, Clementi C, Pasut G, Lin H, Stephens GJ, Whalley BJ, Osborn HMI, Greco F. A novel PEG–haloperidol conjugate with a non-degradable linker shows the feasibility of using polymer–drug conjugates in a non-prodrug fashion. Polym Chem 2016. [DOI: 10.1039/c6py01418f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A PEG–haloperidol conjugate was synthesised, which retains binding to the dopamine D2receptor, showing the possibility of using polymer-drug conjugates as drugsper se' rather than as prodrugs.
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Affiliation(s)
| | | | - Chiara Clementi
- Dept. of Pharmaceutical Sciences
- Via F. Marzolo 5
- University of Padua
- Padova
- Italy
| | - Gianfranco Pasut
- Dept. of Pharmaceutical Sciences
- Via F. Marzolo 5
- University of Padua
- Padova
- Italy
| | - Hong Lin
- Reading School of Pharmacy
- Reading
- UK
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Upadhyay VS, Muntean BS, Kathem SH, Hwang JJ, Aboualaiwi WA, Nauli SM. Roles of dopamine receptor on chemosensory and mechanosensory primary cilia in renal epithelial cells. Front Physiol 2014; 5:72. [PMID: 24616705 PMCID: PMC3935400 DOI: 10.3389/fphys.2014.00072] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 02/06/2014] [Indexed: 01/11/2023] Open
Abstract
Dopamine plays a number of important physiological roles. However, activation of dopamine receptor type-5 (DR5) and its effect in renal epithelial cells have not been studied. Here, we show for the first time that DR5 is localized to primary cilia of LLCPK kidney cells. Renal epithelial cilia are mechanosensory organelles that sense and respond to tubular fluid-flow in the kidney. To determine the roles of DR5 and sensory cilia, we used dopamine to non-selectively and fenoldopam to selectively activate ciliary DR5. Compared to mock treatment, dopamine treated cells significantly increases the length of cilia. Fenoldopam further increases the length of cilia compared to dopamine treated cells. The increase in cilia length also increases the sensitivity of the cells in response to fluid-shear stress. The graded responses to dopamine- and fenoldopam-induced increase in cilia length further show that sensitivity to fluid-shear stress correlates to the length of cilia. Together, our studies suggest for the first time that dopamine or fenoldopam is an exciting agent that enhances structure and function of primary cilia. We further propose that dopaminergic agents can be used in “cilio-therapy” to treat diseases associated with abnormal cilia structure and/or function.
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Affiliation(s)
| | - Brian S Muntean
- Department of Medicinal and Biological Chemistry, The University of Toledo Toledo, OH, USA
| | - Sarmed H Kathem
- Department of Pharmacology, The University of Toledo Toledo, OH, USA ; Department of Pharmacology and Toxicology, College of Pharmacy, University of Baghdad Baghdad, Iraq
| | - Jangyoun J Hwang
- Department of Pharmacology, The University of Toledo Toledo, OH, USA
| | | | - Surya M Nauli
- Department of Pharmacology, The University of Toledo Toledo, OH, USA ; Department of Medicinal and Biological Chemistry, The University of Toledo Toledo, OH, USA
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Mizuta K, Zhang Y, Xu D, Mizuta F, D'Ovidio F, Masaki E, Emala CW. The dopamine D1 receptor is expressed and facilitates relaxation in airway smooth muscle. Respir Res 2013; 14:89. [PMID: 24004608 PMCID: PMC3847358 DOI: 10.1186/1465-9921-14-89] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 08/29/2013] [Indexed: 11/17/2022] Open
Abstract
Background Dopamine signaling is mediated by Gs protein-coupled “D1-like” receptors (D1 and D5) and Gi-coupled “D2-like” receptors (D2-4). In asthmatic patients, inhaled dopamine induces bronchodilation. Although the Gi-coupled dopamine D2 receptor is expressed and sensitizes adenylyl cyclase activity in airway smooth muscle (ASM) cells, the Gs-coupled dopamine D1-like receptor subtypes have never been identified on these cells. Activation of Gs-coupled receptors stimulates cyclic AMP (cAMP) production through the stimulation of adenylyl cyclase, which promotes ASM relaxation. We questioned whether the dopamine D1-like receptor is expressed on ASM, and modulates its function through Gs-coupling. Methods The mRNA and protein expression of dopamine D1-like receptor subtypes in both native human and guinea pig ASM tissue and cultured human ASM (HASM) cells was measured. To characterize the stimulation of cAMP through the dopamine D1 receptor, HASM cells were treated with dopamine or the dopamine D1-like receptor agonists (A68930 or SKF38393) before cAMP measurements. To evaluate whether the activation of dopamine D1 receptor induces ASM relaxation, guinea pig tracheal rings suspended under isometric tension in organ baths were treated with cumulatively increasing concentrations of dopamine or A68930, following an acetylcholine-induced contraction with or without the cAMP-dependent protein kinase (PKA) inhibitor Rp-cAMPS, the large-conductance calcium-activated potassium (BKCa) channel blocker iberiotoxin, or the exchange proteins directly activated by cAMP (Epac) antagonist NSC45576. Results Messenger RNA encoding the dopamine D1 and D5 receptors were detected in native human ASM tissue and cultured HASM cells. Immunoblots confirmed the protein expression of the dopamine D1 receptor in both native human and guinea pig ASM tissue and cultured HASM cells. The dopamine D1 receptor was also immunohistochemically localized to both human and guinea pig ASM. The dopamine D1-like receptor agonists stimulated cAMP production in HASM cells, which was reversed by the selective dopamine D1-like receptor antagonists SCH23390 or SCH39166. A68930 relaxed acetylcholine-contracted guinea pig tracheal rings, which was attenuated by Rp-cAMPS but not by iberiotoxin or NSC45576. Conclusions These results demonstrate that the dopamine D1 receptors are expressed on ASM and regulate smooth muscle force via cAMP activation of PKA, and offer a novel target for therapeutic relaxation of ASM.
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Affiliation(s)
- Kentaro Mizuta
- Departments of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630W 168th St, P&S Box 46, New York, NY 10032, USA.
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Mizuta K, Zhang Y, Xu D, Masaki E, Panettieri RA, Emala CW. The dopamine D(2) receptor is expressed and sensitizes adenylyl cyclase activity in airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2011; 302:L316-24. [PMID: 21964403 DOI: 10.1152/ajplung.00130.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine receptors are G protein-coupled receptors that are divided into two subgroups, "D(1)-like" receptors (D(1) and D(5)) that couple to the G(s) protein and "D(2)-like" receptors (D(2), D(3), and D(4)) that couple to G(i). Although inhaled dopamine has been reported to induce bronchodilation in patients with asthma, functional expression of dopamine receptor subtypes has never been described on airway smooth muscle (ASM) cells. Acute activation of G(i)-coupled receptors inhibits adenylyl cyclase activity and cAMP synthesis, which classically impairs ASM relaxation. In contrast, chronic activation of G(i)-coupled receptors produces a paradoxical enhancement of adenylyl cyclase activity referred to as heterologous sensitization. We questioned whether the dopamine D(2)-like receptor is expressed on ASM, whether it exhibits classical G(i)-coupling, and whether it modulates ASM function. We detected the mRNA encoding the dopamine D(2) receptor in total RNA isolated from native human ASM and from cultured human airway smooth muscle (HASM) cells. Immunoblots identified the dopamine D(2) receptor protein in both native human and guinea pig ASM and cultured HASM cells. The dopamine D(2) receptor protein was immunohistochemically localized to both human and guinea pig ASM. Acute activation of the dopamine D(2) receptor by quinpirole inhibited forskolin-stimulated adenylyl cyclase activity in HASM cells, which was blocked by the dopamine D(2) receptor antagonist L-741626. In contrast, the chronic pretreatment (1 h) with quinpirole potentiated forskolin-stimulated adenylyl cyclase activity, which was inhibited by L-741626, the phospholipase C inhibitor U73122, or the protein kinase C inhibitor GF109203X. Quinpirole also stimulated inositol phosphate synthesis, which was inhibited by L-741626 or U73122. Chronic pretreatment (1 h) of the guinea pig tracheal rings with quinpirole significantly potentiated forskolin-induced airway relaxation, which was inhibited by L-741626. These results demonstrate that functional dopamine D(2) receptors are expressed on ASM and could be a novel therapeutic target for the relaxation of ASM.
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Affiliation(s)
- Kentaro Mizuta
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, New York, New York, USA.
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Jadhav AL, Liu Q. DA1Receptor Mediated Regulation of Na+-H+Antiport Activity in Rat Renal Cortical Brush Border Membrane Vesicles. ACTA ACUST UNITED AC 2009; 14:653-66. [PMID: 1352743 DOI: 10.3109/10641969209036213] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Our previous studies indicate that dopamine (DA) plays an important role in regulating renal sodium (Na+) metabolism during high Na+ intake, and that DA1 receptors are involved in natriuretic response to acute volume expansion. It has also been shown that in addition to the changes in renal hemodynamics, the natriuretic response produced by exogenously administered DA and DA1 receptor agonists appears to be due to alterations in renal tubular sodium transport mechanisms. This study was designed to investigate the DA1 receptor-mediated changes in Na(+)-H+ antiport activity in tubular brush border membranes of rat kidney. The Na(+)-H+ antiport activity, measured as the amiloride-sensitive Na+ influx in BBMV, was inhibited by 37%, 46%, 33%, and 42% by 1 microM DA, SKF 82958, SKF 38393, and fenoldopam respectively. The DA1 antagonist SCH 23390 increased the antiport activity when given alone, while when administered with an agonist it attenuated the effects of the agonist on the antiporter. DA2 agonists and antagonists failed to affect the antiport activity. These results indicate that the inhibitory effects of DA and DA receptor agonists on Na(+)-H+ antiport activity in renal cortical BBMV were mediated by the DA1 receptors.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/analogs & derivatives
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Amiloride/pharmacology
- Animals
- Carrier Proteins/metabolism
- Dopamine/pharmacology
- Dopamine Antagonists
- Fenoldopam
- In Vitro Techniques
- Kidney Cortex/drug effects
- Kidney Cortex/metabolism
- Kinetics
- Male
- Microvilli/metabolism
- Rats
- Rats, Inbred Strains
- Receptors, Dopamine/drug effects
- Receptors, Dopamine/metabolism
- Receptors, Dopamine D1
- Sodium/metabolism
- Sodium-Hydrogen Exchangers
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Affiliation(s)
- A L Jadhav
- College of Pharmacy & Health Sciences, Texas Southern University, Houston 77004
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11
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Abstract
Dopamine plays an important role in regulating renal function and blood pressure. Dopamine synthesis and dopamine receptor subtypes have been shown in the kidney. Dopamine acts via cell surface receptors coupled to G proteins; the receptors are classified via pharmacologic and molecular cloning studies into two families, D1-like and D2-like. Two D1-like receptors cloned in mammals, the D1 and D5 receptors (D1A and D1B in rodents), are linked to adenylyl cyclase stimulation. Three D2-like receptors (D2, D3, and D4) have been cloned and are linked mainly to adenylyl cyclase inhibition. Activation of D1-like receptors on the proximal tubules inhibits tubular sodium reabsorption by inhibiting Na/H-exchanger and Na/K-adenosine triphosphatase activity. Reports exist of defective renal dopamine production and/or dopamine receptor function in human primary hypertension and in genetic models of animal hypertension. In humans with essential hypertension, renal dopamine production in response to sodium loading is often impaired and may contribute to hypertension. A primary defect in D1-like receptors and an altered signaling system in proximal tubules may reduce dopamine-mediated effects on renal sodium excretion. The molecular basis for dopamine receptor dysfunction in hypertension is being investigated, and may involve an abnormal posttranslational modification of the dopamine receptor.
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Affiliation(s)
- Anees Ahmad Banday
- Heart and Kidney Institute, College of Pharmacy, University of Houston, 4800 Calhoun Road, Houston, TX 77204, USA.
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13
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Honegger KJ, Capuano P, Winter C, Bacic D, Stange G, Wagner CA, Biber J, Murer H, Hernando N. Regulation of sodium-proton exchanger isoform 3 (NHE3) by PKA and exchange protein directly activated by cAMP (EPAC). Proc Natl Acad Sci U S A 2006; 103:803-8. [PMID: 16407144 PMCID: PMC1334627 DOI: 10.1073/pnas.0503562103] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Na(+)/H(+) exchanger 3 (NHE3) is expressed in the brush border membrane (BBM) of proximal tubules (PT). Its activity is down-regulated on increases in intracellular cAMP levels. The aim of this study was to investigate the contribution of the protein kinase A (PKA) and the exchange protein directly activated by cAMP (EPAC) dependent pathways in the regulation of NHE3 by adenosine 3',5'-cyclic monophosphate (cAMP). Opossum kidney cells and murine kidney slices were treated with cAMP analogs, which selectively activate either PKA or EPAC. Activation of either pathway resulted in an inhibition of NHE3 activity. The EPAC-induced effect was independent of PKA as indicated by the lack of activation of the kinase and the insensitivity to the PKA inhibitor H89. Both PKA and EPAC inhibited NHE3 activity without inducing changes in the expression of the transporter in BBM. Activation of PKA, but not of EPAC, led to an increase of NHE3 phosphorylation. In contrast, activation of PKA, but not of EPAC, inhibited renal type IIa Na(+)-coupled inorganic phosphate cotransporter (NaPi-IIa), another Na-dependent transporter expressed in proximal BBM. PKA, but not EPAC, induced the retrieval of NaPi-IIa from BBM. Our results suggest that EPAC activation may represent a previously unrecognized mechanism involved in the cAMP regulation of NHE3, whereas regulation of NaPi-IIa is mediated by PKA but not by EPAC.
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Affiliation(s)
- Katharina J Honegger
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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14
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Asghar M, Banday AA, Fardoun RZ, Lokhandwala MF. Hydrogen peroxide causes uncoupling of dopamine D1-like receptors from G proteins via a mechanism involving protein kinase C and G-protein-coupled receptor kinase 2. Free Radic Biol Med 2006; 40:13-20. [PMID: 16337875 DOI: 10.1016/j.freeradbiomed.2005.08.018] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2004] [Revised: 08/08/2005] [Accepted: 08/08/2005] [Indexed: 02/07/2023]
Abstract
Dopamine, via activation of D1-like receptors, inhibits Na,K-ATPase and Na,H-exchanger in renal proximal tubules and promotes sodium excretion. This effect of dopamine is not seen in conditions associated with oxidative stress such as hypertension, diabetes, and aging due to uncoupling of D1-like receptors from G proteins. To identify the role of oxidative stress in uncoupling of the D1-like receptors, we utilized primary cultures from rat renal proximal tubules. Hydrogen peroxide (H2O2), an oxidant, treatment to the cell cultures increased the level of malondialdehyde, a marker of oxidative damage. Further, H2O2 decreased membranous D1-like receptor numbers and proteins, D1-like agonist (SKF 38393)-mediated [35S]GTPgammaS binding and SKF 38393-mediated inhibition of Na,K-ATPase. Moreover, H2O2 treatment to the cultures caused membranous translocation of G-protein-coupled receptor kinase 2 (GRK 2) and increased serine phosphorylation of D1A receptors accompanied by an increase in protein kinase C (PKC) activity. Interestingly, PKC inhibitors blocked the H2O2-mediated stimulation of GRK 2 and serine phosphorylation of D1A receptors. Further, GRK 2 antisense but not scrambled oligonucleotides attenuated the effect of H2O2 on membranous expression of GRK 2. Moreover, direct activation of PKC with phorbol ester (PMA) resulted in reduction of SKF 38393-mediated [35S]GTPgammaS binding. We conclude that H2O2 stimulates PKC leading to the activation of GRK 2, which causes serine phopshorylation of D1A receptors and receptor G-protein uncoupling in these cells, resulting in impairment in D1-like receptor function.
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Affiliation(s)
- Mohammad Asghar
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204, USA
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Bacic D, Capuano P, Baum M, Zhang J, Stange G, Biber J, Kaissling B, Moe OW, Wagner CA, Murer H. Activation of dopamine D1-like receptors induces acute internalization of the renal Na+/phosphate cotransporter NaPi-IIa in mouse kidney and OK cells. Am J Physiol Renal Physiol 2004; 288:F740-7. [PMID: 15547113 PMCID: PMC4133138 DOI: 10.1152/ajprenal.00380.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Na(+)/phosphate cotransporter NaPi-IIa (SLC34A1) is the major transporter mediating the reabsorption of P(i) in the proximal tubule. Expression and activity of NaPi-IIa is regulated by several factors, including parathyroid hormone, dopamine, metabolic acidosis, and dietary P(i) intake. Dopamine induces natriuresis and phosphaturia in vivo, and its actions on several Na(+)-transporting systems such as NHE3 and Na(+)-K(+)-ATPase have been investigated in detail. Using freshly isolated mouse kidney slices, perfused proximal tubules, and cultured renal epithelial cells, we examined the acute effects of dopamine on NaPi-IIa expression and localization. Incubation of isolated kidney slices with the selective D(1)-like receptor agonists fenoldopam (10 microM) and SKF-38393 (10 microM) for 1 h induced NaPi-IIa internalization and reduced expression of NaPi-IIa in the brush border membrane (BBM). The D(2)-like selective agonist quinpirole (1 microM) had no effect. The D(1) and D(2) agonists did not affect the renal Na(+)/sulfate cotransporter NaSi in the BBM of the proximal tubule. Studies with isolated perfused proximal tubules demonstrated that activation of luminal, but not basolateral, D(1)-like receptors caused NaPi-IIa internalization. In kidney slices, inhibition of PKC (1 microM chelerythrine) or ERK1/2 (20 microM PD-098089) pathways did not prevent the fenoldopam-induced internalization. Inhibition with the PKA blocker H-89 (10 microM) abolished the effect of fenoldopam. Immunoblot demonstrated a reduction of NaPi-IIa protein in BBMs from kidney slices treated with fenoldopam. Incubation of opossum kidney cells transfected with NaPi-IIa-green fluorescent protein chimera shifted fluorescence from the apical membrane to an intracellular pool. In summary, dopamine induces internalization of NaPi-IIa by activation of luminal D(1)-like receptors, an effect that is mediated by PKA.
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Affiliation(s)
- Desa Bacic
- Institute of Physiology, Univ. of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland
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16
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Quiñones H, Collazo R, Moe OW. The dopamine precursorl-dihydroxyphenylalanine is transported by the amino acid transporters rBAT and LAT2 in renal cortex. Am J Physiol Renal Physiol 2004; 287:F74-80. [PMID: 15180924 DOI: 10.1152/ajprenal.00237.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The intrarenal autocrine-paracrine dopamine (DA) system is critical for Na+homeostasis. l-Dihydroxyphenylalanine (l-DOPA) uptake from the glomerular filtrate and plasma provides the substrate for DA generation by the renal proximal tubule. The transporter(s) responsible for proximal tubule l-DOPA uptake has not been characterized. Renal cortical poly-A+RNA injected into Xenopus laevis oocytes induced l-DOPA uptake in a time- and dose-dependent fashion with biphasic Kms in the millimolar and micromolar range and independent of inward Na+, K+, or H+gradients, suggesting the presence of low- and high-affinity l-DOPA carriers. Complementary RNA from two amino acid transporters yielded l-DOPA uptake significantly above water-injected controls the rBAT/b0,+AT dimer (rBAT) and the LAT2/4F2 dimer (LAT2). In contradistinction to renal cortical poly-A+, l-DOPA kinetics of rBAT and LAT2 showed classic Michaelis-Menton kinetics with Kms in the micromolar and millimolar range, respectively. Sequence-specific antisense oligonucleotides to rBAT or LAT2 (AS) caused inhibition of rBAT and LAT2 cRNA-induced l-DOPA transport and cortical poly-A+-induced arginine and phenylalanine transport. However, the same ASs only partially blocked poly-A+-induced l-DOPA transport. In cultured kidney cells, silencing inhibitory RNA (siRNA) to rBAT significantly inhibited l-DOPA uptake. We conclude that rBAT and LAT2 can mediate apical and basolateral l-DOPA uptake into the proximal tubule, respectively. Additional l-DOPA transport mechanisms exist in the renal cortex that remain to be identified.
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Affiliation(s)
- Henry Quiñones
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8856, USA.
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17
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Dos Santos EA, Dahly-Vernon AJ, Hoagland KM, Roman RJ. Inhibition of the formation of EETs and 20-HETE with 1-aminobenzotriazole attenuates pressure natriuresis. Am J Physiol Regul Integr Comp Physiol 2004; 287:R58-68. [PMID: 15031141 DOI: 10.1152/ajpregu.00713.2003] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study examined the effects of chronic blockade of the renal formation of epoxyeicosatrienoic acids and 20-hydroxyeicosatetraenoic acid with 1-aminobenzotriazole (ABT; 50 mg·kg−1· day−1ip for 5 days) on pressure natriuresis and the inhibitory effects of elevations in renal perfusion pressure (RPP) on Na+-K+-ATPase activity and the distribution of the sodium/hydrogen exchanger (NHE)-3 in the proximal tubule of rats. In control rats ( n = 15), sodium excretion rose from 2.3 ± 0.4 to 19.4 ± 1.8 μeq·min−1·g kidney weight−1when RPP was increased from 114 ± 1 to 156 ± 2 mmHg. Fractional excretion of lithium rose from 28 ± 3 to 43 ± 3% of the filtered load. Chronic treatment of the rats with ABT for 5 days ( n = 8) blunted the natriuretic response to elevations in RPP by 75% and attenuated the increase in fractional excretion of lithium by 45%. In vehicle-treated rats, renal Na+-K+-ATPase activity fell from 31 ± 5 to 19 ± 2 μmol Pi·mg protein−1·h−1and NHE-3 protein was internalized from the brush border of the proximal tubule after an elevation in RPP. In contrast, Na+-K+-ATPase activity and the distribution of NHE-3 protein remained unaltered in rats treated with ABT. These results suggest that cytochrome P-450 metabolites of arachidonic acid contribute to pressure natriuresis by inhibiting Na+-K+-ATPase activity and promoting internalization of NHE-3 protein from the brush border of the proximal tubule.
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Affiliation(s)
- Elisabete A Dos Santos
- Medical College of Wisconsin, Dept. of Physiology, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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18
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Flournoy WS, Wohl JS, Albrecht-Schmitt TJ, Schwartz DD. Pharmacologic identification of putative D1 dopamine receptors in feline kidneys. J Vet Pharmacol Ther 2003; 26:283-90. [PMID: 12887611 DOI: 10.1046/j.1365-2885.2003.00494.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The presence of dopamine (DA) receptors in feline kidneys is a matter of contention. Radioligand binding and Western blotting studies were employed to determine whether DA receptors are present in feline kidneys. The pharmacologic profile of the selective D1-receptor antagonist [3H]-SCH 23390 was studied in renal cortical membrane preparations from cats by conducting saturation binding isotherm and competitive binding experiments. [3H]-SCH 23390 bound to feline renal cortical membranes in a manner consistent with labeling of a D1-like receptor. The binding profile revealed a single site D1-like or D1 receptor in the feline renal cortex with a Kd = 7.8 +/- 1.0 nmol/L and Bmax = 76.5 +/- 19.5 fmol/mg. Competitive binding studies for [3H]-SCH 23390 against unlabeled agonists yielded the following Ki values and rank order of competition: SKF38393 (Ki = 0.47 +/- 0.26 micro m) > fenoldopam (Ki = 3.12 +/- 1.1 micro m) > DA (Ki = 933.1 +/- 1.6 micro m). Competitive binding studies for [3H]-SCH-23390 against unlabeled antagonists yielded the following rank order of competition: SCH 23390 (Ki = 1.97 +/- 0.81 micro m) > spiperone (Ki = 3.79 +/- 0.79) > metoclopramide (Ki = 4.26 +/- 2.4 micro m). Western blot analysis with anti-DA D1 receptor antibodies detected a single band with Mr of 74 kDa corresponding to a D1 DA receptor. These results suggest that a putative D1-like or D1 receptor exists in feline kidneys different from those previously identified in rat, dog or human kidneys.
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Affiliation(s)
- W S Flournoy
- Walter Reed Army Institute of Research, Washington DC, USA
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19
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Zheng S, Yu P, Zeng C, Wang Z, Yang Z, Andrews PM, Felder RA, Jose PA. Galpha12- and Galpha13-protein subunit linkage of D5 dopamine receptors in the nephron. Hypertension 2003; 41:604-10. [PMID: 12623966 DOI: 10.1161/01.hyp.0000057422.75590.d7] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The roles of the G-protein alpha-subunits, Gs, Gi, and Gq/11, in the signal transduction of the D1-like dopamine receptors, D1 and D5, have been deciphered. Galpha12 and Galpha13, members of the 4th family of G protein subunits, are not linked with D1 receptors, and their linkage to D5 receptors is not known. Therefore, we studied the expression of Galpha12 and Galpha13 and interaction with D5 dopamine receptors in the kidney from normotensive Wistar-Kyoto (WKY) rats and D5 receptor-transfected HEK293 cells. Galpha12 and Galpha13 were found in the proximal tubule, distal convoluted tubule, and artery and vein in the WKY rat kidney. Whereas Galpha12 was expressed in the ascending limb of Henle, Galpha13 was expressed in the collecting duct and juxtaglomerular cells. In renal proximal tubules, Galpha12 and Galpha13, as with D5 receptors, were expressed in brush border membranes. Laser confocal microscopy revealed the colocalization of D5 receptors with Galpha12 and Galpha13 in rat renal brush border membranes, immortalized rat renal proximal tubule cells, and D5 receptor-transfected HEK293 cells. In these cells, a D1-like agonist, fenoldopam, increased the association of Galpha12 and Galpha13 with D5 receptors, results that were corroborated by immunoprecipitation experiments. We conclude that although both D1 and D5 receptors are linked to Galphas, they are differentially linked to Galpha12 and Galpha13. The consequences of the differential G-protein subunit linkage on D1- and D5-mediated sodium transport remains to be determined.
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Affiliation(s)
- Shaopeng Zheng
- Department of Pediatrics, Georgetown University Medical Center, 3800 Reservoir Road, NW, Washington, DC 20007, USA
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20
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Abstract
Dopamine has been recognized as an important modulator of central as well as peripheral physiologic functions in both humans and animals. Dopamine receptors have been identified in a number of organs and tissues, which include several regions within the central nervous system, sympathetic ganglia and postganglionic nerve terminals, various vascular beds, the heart, the gastrointestinal tract, and the kidney. The peripheral dopamine receptors influence cardiovascular and renal function by decreasing afterload and vascular resistance and promoting sodium excretion. Within the kidney, dopamine receptors are present along the nephron, with highest density on proximal tubule epithelial cells. It has been reported that there is a defective dopamine receptor, especially D(1) receptor function, in the proximal tubule of various animal models of hypertension as well as in humans with essential hypertension. Recent reports have revealed the site of and the molecular mechanisms responsible for the defect in D(1) receptors in hypertension. Moreover, recent studies have also demonstrated that the disruption of various dopamine receptor subtypes and their function produces hypertension in rodents. In this review, we present evidence that dopamine and dopamine receptors play an important role in regulating renal sodium excretion and that defective renal dopamine production and/or dopamine receptor function may contribute to the development of various forms of hypertension.
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Affiliation(s)
- Tahir Hussain
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, Texas 77204, USA
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21
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Umrani DN, Banday AA, Hussain T, Lokhandwala MF. Rosiglitazone treatment restores renal dopamine receptor function in obese Zucker rats. Hypertension 2002; 40:880-5. [PMID: 12468573 DOI: 10.1161/01.hyp.0000039963.01288.d3] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Earlier we have reported a defective dopamine D1-like receptor function, which was accompanied by a decrease in D1 receptor numbers and the inability of dopamine to inhibit Na,K-ATPase and Na,H-exchanger in proximal tubules of hyperinsulinemic obese Zucker rats. The present study was designed to test the hypothesis that the defect in dopamine receptor function is a result of hyperinsulinemia in obese rats. We designed experiments to study D1 receptor function in obese Zucker rats treated with rosiglitazone, as it lowers plasma insulin by improving insulin sensitivity. A group of untreated lean and obese rats served as controls. Rosiglitazone treatment (10 mg/kg orally, 4 weeks) caused significant decreases in plasma insulin, blood glucose, and blood pressure while causing an increase in renal sodium excretion compared with untreated obese rats. In the isolated proximal tubules obtained from untreated lean rats, dopamine caused concentration-dependent inhibition of the Na,K-ATPase activity, but this inhibitory effect was absent in untreated obese rats. In rosiglitazone-treated obese rats, the inhibitory effect of dopamine on Na,K-ATPase was significantly restored. This was accompanied by a complete restoration of D1 receptor numbers in proximal tubular membranes of treated obese rats. In another set of experiments, treatment of primary proximal tubule epithelial cells in culture medium with insulin caused a significant decrease in the D1 receptor abundance, suggesting a direct role of insulin on D1 receptor regulation. We conclude that hyperinsulinemia causes downregulation of D1 receptor function and lowering of plasma insulin levels leads to restoration of renal D1 receptor function.
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Affiliation(s)
- Dhananjay N Umrani
- Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, Tex 77204, USA
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22
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Gomes P, Soares-da-Silva P. Dopamine-induced inhibition of Na+-K+-ATPase activity requires integrity of actin cytoskeleton in opossum kidney cells. ACTA PHYSIOLOGICA SCANDINAVICA 2002; 175:93-101. [PMID: 12028129 DOI: 10.1046/j.1365-201x.2002.00972.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study evaluated the importance of the association between Na+-K+-ATPase and the actin cytoskeleton on dopamine-induced inhibition of Na+-K+-ATPase activity. The approach used measures the transepithelial transport of Na+ in monolayers of opossum kidney (OK) cells, when the Na+ delivered to Na+-K+-ATPase was increased at the saturating level by amphotericin B. The maximal amphotericin B (1.0 microg mL-1) induced increase in short-circuit current (Isc) was prevented by ouabain (100 microM) or removal of apical Na+. Dopamine (1 microM) applied from the apical side significantly decreased (29 +/- 5% reduction) the amphotericin B-induced increase in Isc, this being prevented by the D1-like receptor antagonist SKF 83566 (1 microM) and the protein kinase C (PKC) inhibitor chelerythrine (1 microM). Exposure of OK cells to cytochalasin B (1 microM) or cytochalasin D (1 microM), inhibitors of actin polymerization, from both cell sides reduced by 31 +/- 4% and 36 +/- 3% the amphotericin B-induced increase in Isc and abolished the inhibitory effect of apical dopamine (1 microM), but not that of the PKC activator phorbol-12,13-dibutyrate (PDBu; 100 nM). Colchicine (1 microM) failed to alter the inhibitory effects of dopamine. The relationship between Na+-K+-ATPase and the concentration of extracellular Na+ showed a Michaelis-Menten constant (Km) of 44.1 +/- 13.7 mM and a Vmax of 49.6 +/- 4.8 microA cm-2 in control monolayers. In the presence of apical dopamine (1 microM) or cytochalasin B (1 microM) Vmax values were significantly (P < 0.05) reduced without changes in Km values. These results are the first, obtained in live cells, showing that the PKC-dependent inhibition of Na+-K+-ATPase activity by dopamine requires the integrity of the association between actin cytoskeleton and Na+-K+-ATPase.
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Affiliation(s)
- P Gomes
- Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal
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23
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Hussain T, Becker M, Beheray S, Lokhandwala MF. Dopamine fails to inhibit Na,H-exchanger in proximal tubules of obese Zucker rats. Clin Exp Hypertens 2001; 23:591-601. [PMID: 11728004 DOI: 10.1081/ceh-100107389] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Dopamine via the activation of D1-like receptors inhibits Na,K-ATPase and Na,H-exchanger and subsequently increases sodium excretion. We have previously reported that dopamine failed to inhibit Na,K-ATPase in the proximal tubules (PTs) of obese Zucker rats. The present study was designed to determine the effect of dopamine on Na,H-exchanger in PTs of lean and obese Zucker rats, and examine D1-like receptor-coupled signal transduction pathway mediating the inhibition of Na,H-exchanger. We found that dopamine inhibited Na,H-exchanger in the PTs of lean rats but this response was absent in obese rats. In brush border membranes, [3H]SCH 23390 binding revealed a approximately 45% reduction in D1-like receptor binding sites in obese compared to lean rats. Dopamine stimulated cAMP accumulation in PTs of lean but not in obese rats. Forskolin-mediated stimulation of cAMP was similar in lean and obese rats. Dopamine as well as forskolin and dibutyryl cAMP-mediated stimulation of protein kinase A (PKA) was reduced in PTs of obese compared to lean rats. The data suggest that reduction in D1-like receptor binding sites, defective coupling with signaling pathway and inability of PKA activation may be responsible for the failure of dopamine to inhibit Na,H-exchanger in PTs of obese rats. This phenomenon may contribute to an increase in sodium reabsorption and development of hypertension in obese Zucker rats.
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Affiliation(s)
- T Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, TX 77204, USA
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24
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Cerrutti JA, Quaglia NB, Torres AM. Characterization of the mechanisms involved in the gender differences in p-aminohippurate renal elimination in rats. Can J Physiol Pharmacol 2001. [DOI: 10.1139/y01-048] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gender differences in the renal handling on drugs and toxins have received too little attention. In the present study, a variety of preparations were used to examine the basis for the greater effectiveness of the male kidneys in the elimination of p-aminohippurate (PAH) in rats. Renal clearance of PAH was significantly lower in female rats as consequence of its smaller filtered and secreted load. The gender difference in the filtered load may be accounted for the lower value of glomerular filtration rate (GFR) displayed by female rats as compared with males. The lower value of the renal blood flow observed in females might explain, at least in part, the decrease in the GFR and in the secreted load of PAH. In females, maximal uptake for PAH transport into renal basolateral membrane vesicles decreased to 52 ± 9 % (P < 0.05) and Michaelis-Menten constant for PAH uptake into renal brush border membrane vesicles was increased to 163 ± 8 % (P < 0.05). These changes might also explain the lower secreted load of PAH. The sex difference in the renal clearance of PAH was also evidenced by the reduced systemic clearance observed in female rats.Key words: organic anions, transport in renal membrane vesicles, renal clearance, systemic clearance, sex.
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25
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Narkar VA, Hussain T, Pedemonte C, Lokhandwala MF. Dopamine D(2) receptor activation causes mitogenesis via p44/42 mitogen-activated protein kinase in opossum kidney cells. J Am Soc Nephrol 2001; 12:1844-1852. [PMID: 11518777 DOI: 10.1681/asn.v1291844] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
This study was conducted to determine the expression of dopamine D(2)-like receptors in opossum kidney (OK) cells and to examine the potential role of these receptors in mitogenesis. First, the presence of D(2)-like receptor binding sites in OK cell membranes was demonstrated by radioligand binding, using [(3)H]spiperone. The D(2)-like receptor subtypes expressed in OK cells were subsequently demonstrated, by Western blotting, to be D(2), D(3), and D(4) receptors. OK cells were stimulated with bromocriptine, (+/-)-2-(N-phenylethyl-N-propyl)amino-5-hydroxytetralin hydrochloride, (R)-(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide, or PD 168,077 maleate (D(2)-like, D(2), D(3), and D(4) receptor agonists, respectively), and mitogenesis was measured as a function of [(3)H]thymidine incorporation. It was observed that, whereas bromocriptine and (+/-)-2-(N-phenylethyl-N-propyl)amino-5-hydroxytetralin hydrochloride produced increases in [(3)H]thymidine incorporation, (R)-(+)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide and PD 168,077 maleate did not produce such an effect, indicating the involvement of D(2) receptors in the mitogenic response. Pertussis toxin and PD 98059 blocked the mitogenesis caused by bromocriptine, suggesting a role for G(i) or G(o) proteins and p44/42 mitogen-activated protein kinase (MAPK), respectively. Furthermore, it was observed that bromocriptine produced a time-dependent increase in the phosphorylation (activation) of p44/42 MAPK, which was blocked by domperidone, pertussis toxin, or PD 98059. Therefore, this study demonstrates that, although OK cells express D(2), D(3), and D(4) receptors, activation of only D(2) receptors causes mitogenesis via phosphorylation of p44/42 MAPK. Furthermore, the cellular mechanisms contributing to D(2) receptor-mediated phosphorylation of p44/42 MAPK seem to involve the tyrosine kinase, phosphatidylinositol-3-kinase, and protein kinase C pathways. It is likely that bromocriptine and other preferential D(2) receptor agonists might provide protection against ischemic reperfusion injury in renal proximal tubular cells, by increasing the survival rates for ischemic cells.
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Affiliation(s)
- Vihang A Narkar
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Tahir Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Carlos Pedemonte
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
| | - Mustafa F Lokhandwala
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Texas
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26
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Bek MJ, Zheng S, Xu J, Yamaguchi I, Asico LD, Sun XG, Jose PA. Differential expression of adenylyl cyclases in the rat nephron. Kidney Int 2001; 60:890-9. [PMID: 11532084 DOI: 10.1046/j.1523-1755.2001.060003890.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Adenylyl cyclases (ACs) are a family of enzymes that catalyze the formation of the second-messenger cyclic adenosine 3',5'-monophosphate (cAMP). At least nine isoforms of AC have been cloned. These isoforms differ in their tissue distribution and basal activity. AC isoforms also differ in their capacity to be stimulated or inhibited by G protein alpha(i), alpha(s) and beta/gamma subunits, protein kinase C, and intracellular calcium. The distribution of ACs in the kidney is only partially known, although it is known that ACs play important roles in kidney signal transduction. Several receptors are known to couple to AC, but their linkage to individual AC isoforms in the kidney is not known. METHODS This study investigated the tissue distribution of AC isoforms along the nephron of Wistar-Kyoto rats using reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and immunoblotting. RESULTS While AC VI and IX mRNA were found in all nephron segments, there was no expression of AC VIII mRNA. ACs II through V and VII mRNA were variably found in specific nephron segments. mRNA for AC isoforms II, III, VI, VII, and IX were expressed in renal proximal tubules. All of the AC isoforms studied, except VIII, were found in glomeruli. Immunoblotting and immunohistochemistry confirmed the mRNA results. AC isoforms II, III, IV, and IX were expressed in luminal rather than in basolateral membranes. However, immunohistochemical studies were not feasible for the other isoforms that could be expressed in basolateral membranes. CONCLUSION Knowledge of the distribution of ACs may help establish the linkage between receptors and specific AC isoforms and define their functions.
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Affiliation(s)
- M J Bek
- Department of Pediatrics, Georgetown University Medical Center, Washington, DC 20007, USA
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27
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Hu MC, Fan L, Crowder LA, Karim-Jimenez Z, Murer H, Moe OW. Dopamine acutely stimulates Na+/H+ exchanger (NHE3) endocytosis via clathrin-coated vesicles: dependence on protein kinase A-mediated NHE3 phosphorylation. J Biol Chem 2001; 276:26906-15. [PMID: 11328806 DOI: 10.1074/jbc.m011338200] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dopamine (DA) is a key hormone in mammalian sodium homeostasis. DA induces natriuresis via acute inhibition of the renal proximal tubule apical membrane Na(+)/H(+) exchanger NHE3. We examined the mechanism by which DA inhibits NHE3 in a renal cell line. DA acutely decreases surface NHE3 antigen in dose- and time-dependent fashion without altering total cellular NHE3. Although DA(1) receptor agonist alone decreases surface NHE3, simultaneous DA(2) agonist synergistically enhances the effect of DA(1). Decreased surface NHE3 antigen, caused by stimulation of NHE3 endocytosis, is dependent on intact functioning of the GTPase dynamin and involves increased binding of NHE3 to the adaptor protein AP2. DA-stimulated NHE3 endocytosis can be blocked by pharmacologic or genetic protein kinase A inhibition or by mutation of two protein kinase A target serines (Ser-560 and Ser-613) on NHE3. We conclude that one mechanism by which DA induces natriuresis is via protein kinase A-mediated phosphorylation of proximal tubule NHE3 leading to endocytosis of NHE3 via clathrin-coated vesicles.
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Affiliation(s)
- M C Hu
- Medical Service, Department of Veterans Affairs Medical Center, Dallas, Texas 75216, USA
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28
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Odlind C, Fasching A, Liss P, Palm F, Hansell P. Changing dopaminergic activity through different pathways: consequences for renal sodium excretion, regional blood flow and oxygen tension in the rat. ACTA PHYSIOLOGICA SCANDINAVICA 2001; 172:219-26. [PMID: 11472309 DOI: 10.1046/j.1365-201x.2001.00852.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dopamine (DA) is an intrarenal natriuretic hormone involved in sodium homeostasis, but the regulation of renal dopaminergic tonus is unclear. We evaluated different pathways for elevating DA tonus to determine which are important for the ability of the kidney to produce natriuresis and studied the accompanying effects on regional renal blood flow and oxygen tension. Thus, we compared the effects of a catechol-O-methyl transferase (COMT)-inhibitor, an unspecific monoamine oxidase (MAO)-inhibitor, a D1-like receptor agonist and a DA precursor in anaesthetized rats. Sodium excretion increased sixfold after COMT inhibition, eightfold after administration of the D1-like agonist, whereas it was similar to control after MAO inhibition and infusion of DA precursor. Urinary dopamine excretion increased 42% by COMT inhibition, 55% by MAO inhibition and 12-fold after DA precursor, but remained unchanged after infusion of the D1-like agonist. The D1-like receptor agonist led to a 38% increase in the cortical blood flow and a 21% increase in outer medullary blood flow. Regional renal blood flow was unaffected by all other treatments. Cortical and outer medullary oxygen tension was unaffected in all treatment groups. To conclude, the natriuretic and haemodynamic properties of an elevation in DA tonus depends on the route by which the elevation occurred. Systemic administration of a D1-like receptor agonist, results in a natriuretic response which, as opposed to the natriuresis seen after COMT inhibition, coincides with an increase in renal cortical and outer medullary blood flow. Precursor delivery or MAO inhibition did not change neither urinary sodium excretion nor renal blood flow.
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Affiliation(s)
- C Odlind
- Department of Physiology, Biomedical Centre, University of Uppsala, Uppsala, Sweden
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Saito O, Ando Y, Kusano E, Asano Y. Functional characterization of basolateral and luminal dopamine receptors in rabbit CCD. Am J Physiol Renal Physiol 2001; 281:F114-22. [PMID: 11399652 DOI: 10.1152/ajprenal.2001.281.1.f114] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies reported the existence of both D1- and D2-like receptors in the cortical collecting duct (CCD). However, especially with regard to natriuresis, it remains controversial. In the present study, rabbit CCD was perfused to characterize the receptor subtypes responsible for the tubular actions. Basolateral dopamine (DA) induced a dose-dependent depolarization of transepithelial voltage. Basolateral domperidone, a D2-like receptor antagonist, abolished depolarization, whereas SKF-81297, a D1-like receptor agonist, showed no significant change. In addition, bromocriptine, a D2-like receptor agonist, also caused depolarization, whereas SKF-81297, a D1-like receptor agonist, did not depolarize significantly. Moreover, RBI-257, a D4-specific antagonist, reversed the basolateral DA-induced depolarization. In contrast to the basolateral side, luminal DA caused depolarization via a D1-like receptor; however the change was less than that for basolateral DA. For further evaluation, 22Na+ flux (J(Na)) was measured to confirm the effect of DA on Na+ transport. Basolateral DA also caused a suppression of J(Na), and this reaction was abolished by domperidone. These results suggested that the basolateral D2-like receptor is mainly responsible for the natriuretic action of DA in rabbit CCD.
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Affiliation(s)
- O Saito
- Division of Nephrology, Department of Medicine, Jichi Medical School, Tochigi 329-0498, Japan
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Féraille E, Doucet A. Sodium-potassium-adenosinetriphosphatase-dependent sodium transport in the kidney: hormonal control. Physiol Rev 2001; 81:345-418. [PMID: 11152761 DOI: 10.1152/physrev.2001.81.1.345] [Citation(s) in RCA: 340] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Tubular reabsorption of filtered sodium is quantitatively the main contribution of kidneys to salt and water homeostasis. The transcellular reabsorption of sodium proceeds by a two-step mechanism: Na(+)-K(+)-ATPase-energized basolateral active extrusion of sodium permits passive apical entry through various sodium transport systems. In the past 15 years, most of the renal sodium transport systems (Na(+)-K(+)-ATPase, channels, cotransporters, and exchangers) have been characterized at a molecular level. Coupled to the methods developed during the 1965-1985 decades to circumvent kidney heterogeneity and analyze sodium transport at the level of single nephron segments, cloning of the transporters allowed us to move our understanding of hormone regulation of sodium transport from a cellular to a molecular level. The main purpose of this review is to analyze how molecular events at the transporter level account for the physiological changes in tubular handling of sodium promoted by hormones. In recent years, it also became obvious that intracellular signaling pathways interacted with each other, leading to synergisms or antagonisms. A second aim of this review is therefore to analyze the integrated network of signaling pathways underlying hormone action. Given the central role of Na(+)-K(+)-ATPase in sodium reabsorption, the first part of this review focuses on its structural and functional properties, with a special mention of the specificity of Na(+)-K(+)-ATPase expressed in renal tubule. In a second part, the general mechanisms of hormone signaling are briefly introduced before a more detailed discussion of the nephron segment-specific expression of hormone receptors and signaling pathways. The three following parts integrate the molecular and physiological aspects of the hormonal regulation of sodium transport processes in three nephron segments: the proximal tubule, the thick ascending limb of Henle's loop, and the collecting duct.
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Affiliation(s)
- E Féraille
- Division of Nephrology, Geneva University Hospital, Geneva, Switzerland.
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31
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Wiederkehr MR, Di Sole F, Collazo R, Quiñones H, Fan L, Murer H, Helmle-Kolb C, Moe OW. Characterization of acute inhibition of Na/H exchanger NHE-3 by dopamine in opossum kidney cells. Kidney Int 2001; 59:197-209. [PMID: 11135072 DOI: 10.1046/j.1523-1755.2001.00480.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Dopamine (DA) is a principal natriuretic hormone that defends extracellular fluid volume from a Na load. Natriuresis is effected partly through inhibiting the proximal tubule Na/H exchanger NHE-3. Changes in NHE-3 phosphorylation is one mechanism by which NHE-3 activity is regulated. METHODS We used opossum kidney (OK) cells to characterize the differential and synergistic effects of DA receptor subtype-1 (DA1) and -2 (DA2) agonists and the effect of blockade of protein kinase A (PKA) or protein kinase C (PKC) on NHE-3 activity and phosphorylation. RESULTS DA and DA1 agonists inhibited NHE-3 activity, and DA1 antagonist blocked the effect of either DA or DA1 agonist. DA2 agonist alone had no effect, but DA2 antagonist reduced the DA effect on NHE-3 activity. DA1 and DA2 agonists together were more potent than DA1 alone. PKA inhibition eliminated the effect of DA1 agonist and partially blocked the effect of DA on NHE-3 activity. PKC inhibition did not block the DA effect. DA1 agonist and PKA activation phosphorylated NHE-3 on identical sites. Despite lack of effect on NHE-3 activity, DA2 agonists increased NHE-3 phosphorylation. DA-induced NHE-3 phosphorylation was distinct from DA1 and PKA but closely resembled DA2. CONCLUSION We postulate the following: (1) DA modifies NHE-3 phosphorylation by activating PKA through DA1 and by other kinases/phosphatases via DA2. (2) DA1 is sufficient to inhibit NHE-3, while DA2 is insufficient but plays a synergistic role by altering NHE-3 phosphorylation.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Bromocriptine/pharmacology
- Cells, Cultured
- Cyclic AMP/pharmacology
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Dopamine/pharmacology
- Dopamine Agonists/pharmacology
- Dose-Response Relationship, Drug
- Kidney/cytology
- Kidney/metabolism
- Opossums
- Phosphorylation
- Protein Kinase C/metabolism
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/agonists
- Receptors, Dopamine D2/metabolism
- Sodium-Hydrogen Exchanger 3
- Sodium-Hydrogen Exchangers/antagonists & inhibitors
- Time Factors
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Affiliation(s)
- M R Wiederkehr
- Medical Service, Department of Veteran Affairs Medical Center and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235-8856, USA
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32
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Alpern RJ. Endocrine Control of Acid‐Base Balance. Compr Physiol 2000. [DOI: 10.1002/cphy.cp070315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
Diuretics are the mainstay of traditional therapy for congestive heart failure. The syndrome of heart failure is now understood to involve complex interactions of neurohumoral substances released in response to poor cardiac function. Developmental changes during infancy and childhood will affect both the activation of systemic neurohumoral responses and the pharmacokinetic and pharmacodynamic actions of diuretics. Few human studies directly evaluate the efficacy of diuretic therapy in heart failure in adults. The pharmacodevelopmental aspects of diuretic therapy in infants and children are also incompletely studied. This review will describe the kidney's role in the pathogenesis of sodium and water retention in heart failure and the developmental changes in the kidney related to fluid retention. Known principles of diuretic therapy in congestive heart failure will be described. All these factors can then be used by the reader to evaluate the role of diuretic therapy in the complex syndrome of heart failure in infants and children.
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Beheray SA, Hussain T, Lokhandwala MF. Dopamine inhibits na,h-exchanger via D1-like receptor-mediated stimulation of protein kinase a in renal proximal tubules. Clin Exp Hypertens 2000; 22:635-44. [PMID: 10972167 DOI: 10.1081/ceh-100100097] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Dopamine causes natriuresis and diuresis via activation of D1-like receptors located in the renal proximal tubules. It is reported that this response to dopamine results from the inhibition of Na,H-exchanger and Na,K-ATPase. Earlier studies have suggested a role of protein kinase A (PKA) in the inhibition of Na,H-exchanger, however, the effect of dopamine or the dopamine receptor subtype responsible for the stimulation of PKA has not been reported. Present study was designed to examine the effect of dopamine and D1-like receptor agonist, SKF 38393, on the stimulation of PKA activity in rat renal proximal tubules. Dopamine and SKF 38393 (1 nM - 1 microM) caused stimulation of PKA activity, an effect which was antagonized by a D1-like receptor antagonist, SCH 23390 (10 microM). Stimulation of PKA activity was also seen with forskolin and di-butyryl cAMP. We also observed that dopamine and SKF 38393 inhibited Na,H-exchanger activity in the proximal tubules. This response was blocked by SCH 23390 and Rp-cAMPS triethylamine, a selective inhibitor of PKA. Similarly, forskolin and di-butyryl cAMP inhibited Na,H-exchanger activity. The data provide direct evidence showing that dopamine, through the activation of D1-like receptors stimulates PKA activity which in turn inhibits Na,H-exchanger in the proximal tubules.
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Affiliation(s)
- S A Beheray
- Institute for Cardiovascular Studies College of Pharmacy, University of Houston, TX 77204-5511, USA
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35
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Beheray S, Kansra V, Hussain T, Lokhandwala MF. Diminished natriuretic response to dopamine in old rats is due to an impaired D1-like receptor-signaling pathway. Kidney Int 2000; 58:712-20. [PMID: 10916094 DOI: 10.1046/j.1523-1755.2000.00217.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Dopamine (DA) causes natriuresis and diuresis, which results from activation of D1-like receptor (D1R) located on proximal tubules. Earlier, we reported that DA failed to inhibit Na,K-ATPase in proximal tubules of old Fischer 344 rats. The present study was designed to investigate the functional consequence of this phenomenon. METHODS Measurements of the functional (natriuretic and diuretic) response to intravenously infused DA and SKF 38393 (D1R agonist) in adult (6 month) and old (24 month) Fischer 344 rats were taken. Biochemical measurements were carried out to determine the potential defects in D1R and its signaling pathway in proximal tubules of old rats. RESULTS We found that intravenous infusion of DA and SKF 38393 caused natriuresis and diuresis in adult rats, but this response was blunted in old rats. In the isolated proximal tubules, DA and SKF 38393 inhibited Na,H-exchanger (NHE) in adult rats; however, this inhibition was attenuated in old rats. Radioligand binding revealed approximately 46% reduction in D1R binding sites in brush border membranes (BBMs) in old compared with adult rats. SKF 38393 stimulated [35S]GTPgammaS binding in BBM in adult rats, but not in old rats, suggesting an impaired D1R-G protein coupling. DA and SKF 38393 stimulated adenylyl cyclase (AC) activity in adult but not in the old rats. Forskolin and NaF stimulated AC activity in a comparable manner in adult and old rats, indicating no defect in AC and G proteins. DA and SKF 38393 failed to stimulate protein kinase A (PKA) activity in proximal tubules of old rats. Dibutyryl-cAMP-mediated PKA activation was also absent in old rats. CONCLUSIONS A decrease in D1R binding sites, a coupling defect with G proteins, and a defect in PKA activation lead to diminished DA-mediated inhibition of NHE in old rats, which may contribute to the blunted natriuretic response to DA in these animals.
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Affiliation(s)
- S Beheray
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, TX 77204-5511, USA
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36
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O'Connell DP, Aherne AM. Renal dopaminergic mechanisms and hypertension: a chronology of advances. Clin Exp Hypertens 2000; 22:217-49. [PMID: 10803730 DOI: 10.1081/ceh-100100074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Dopamine (DA) has been shown to influence kidney function through endogenous synthesis and subsequent interaction with locally expressed dopamine receptor subtypes (D1, D5 as D1-like and D2, D3, and D4 as D2-like). DA, and DA-receptor specific agonists and antagonists can alter renal water and electrolyte excretion along with renin release when infused systemically or intrarenally. Such effects are brought about by a combination of renal hemodynamic and direct tubular effects evoked along the full length of the nephron. The cellular mechanisms that direct these dopamine-mediated renal electrolyte fluxes have recently been clarified and include alterations in adenylyl cyclase, phospholipase C, and phospholipase A1 activity. The dopaminergic system also interacts directly with the renal kallikrein-kinin, prostaglandin and other neurohumoral systems. Aberrant renal dopamine production and/or dopamine receptor function have been reported in salt-dependent and low-renin forms of human primary hypertension as well as in genetic models of animal hypertension, including the SHR and Dahl SS rat. DA D1 or D3 receptor knockout mice have been shown to develop hypertension.
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Affiliation(s)
- D P O'Connell
- Department of Pharmacology & Therapeutics, University College Cork, Ireland
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Berndt TJ, Tucker RR, Kent PD, Streiff PC, Tyce GM, Knox FG. Dopamine enhances the phosphaturic effect of PTH during acute respiratory alkalosis. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1999; 134:616-22. [PMID: 10595790 DOI: 10.1016/s0022-2143(99)90102-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The phosphaturic response to parathyroid hormone (PTH) is blunted during acute respiratory alkalosis. The objective of the present study was to determine the effect of dopamine on the blunted phosphaturic response to PTH during acute respiratory alkalosis. The phosphaturic response to PTH was determined in thyroparathyroidectomized (TPTX) normocapnic and respiratory alkalotic rats in the absence and presence of the infusion of exogenous dopamine (25 microg/kg/min) or of 3,4-dihydroxyphenylalanine (L-DOPA, 250 microg/kg/min) to increase endogenous dopamine synthesis. In normocapnic rats, PTH infusion (33 U/kg plus 1 U/kg/min) significantly increased the fractional excretion of phosphate (FE(Pi)), from 1.5%+/-0.5% to 28.4%+/-4.0%, (deltaFE(Pi) 26.9%+/-4.1%, n = 11, P<.05); in respiratory alkalotic rats, the increase was from 0.4%+/-0.1% to 11.4%+/-1.7% (deltaFE(Pi) 11.0%+/-1.8%, n = 13, P<.05). However, the phosphaturic response to PTH was attenuated in respiratory alkalotic rats (deltaFE(Pi) 26.9%+/-4.1% vs 11.0%+/-1.9%, P<.05). In normocapnic rats, in the presence of dopamine or L-DOPA infusions, PTH infusion significantly increased the FE(Pi) from 6.1%+/-2.3% to 33.4%+/-8.0% (deltaFE(Pi) 27.3%+/-7.0%, n = 5) and from 3.2%+/-0.6% to 32.5%+/-3.3% (deltaFE(Pi) 29.3%+/-3.2%, n = 7), respectively. In respiratory alkalotic rats, in the presence of dopamine infusion, PTH significantly increased the FE(Pi), from 0.6%+/-0.2% to 19.3%+/-3.3% (deltaFE(Pi) 18.7%+/-3.3%, n = 6); in the presence of L-DOPA infusion it increased from 1.0%+/-0.3% to 20.5%+/-2.8% (deltaFE(Pi) 19.5%+/-2.9%, n = 8, P<.05 as compared with PTH alone). Thus the phosphaturic effect of PTH that was attenuated in respiratory alkalotic rats was enhanced by stimulation of endogenous dopamine synthesis by the infusion of L-DOPA.
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Affiliation(s)
- T J Berndt
- Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, MN 55905, USA
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38
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Barnard ML, Ridge KM, Saldias F, Friedman E, Gare M, Guerrero C, Lecuona E, Bertorello AM, Katz AI, Sznajder JI. Stimulation of the dopamine 1 receptor increases lung edema clearance. Am J Respir Crit Care Med 1999; 160:982-6. [PMID: 10471628 DOI: 10.1164/ajrccm.160.3.9812003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We previously reported that lung edema clearance was stimulated by dopamine (DA). The purpose of this study was to determine whether the DA-mediated stimulation of edema clearance occurs via an adrenergic or dopaminergic regulation of alveolar epithelial Na, K-ATPase. When isolated perfused rat lungs were coinstilled with DA and SCH 23390 (a specific D(1) receptor antagonist), there was a dose-dependent attenuation of the stimulatory effects of DA. Coinstillation with S-sulpiride (a specific D(2) receptor antagonist) or propranolol (a beta-adrenergic antagonist) did not alter DA-stimulated clearance. Similarly, the specific dopaminergic D(1) agonist fenoldopam increased lung edema clearance, but quinpirole (a specific dopaminergic D(2) agonist) did not. (125)I-SCH 23982 binding studies suggested that D(1) receptors are expressed on alveolar type II (ATII) cells with an apparent dissociation constant (K(d)) of 4.4 nM and binding maximum (Bmax) 9.8 pmol/mg. Consistent with these results, the D(1) receptor messenger RNA (mRNA) and protein were detected in ATII cells by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. These data demonstrate a novel mechanism involving the activation of dopaminergic D(1) receptors which mediates DA-stimulated edema removal from rat lungs.
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Affiliation(s)
- M L Barnard
- Michael Reese Hospital and Medical Center, Pulmonary and Critical Care Medicine and Northwestern University Medical School, Chicago, Illinois, USA
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de Toledo FG, Thompson MA, Bolliger C, Tyce GM, Dousa TP. gamma-L-glutamyl-L-DOPA inhibits Na(+)-phosphate cotransport across renal brush border membranes and increases renal excretion of phosphate. Kidney Int 1999; 55:1832-42. [PMID: 10231445 DOI: 10.1046/j.1523-1755.1999.00419.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND For treatment of phosphate (Pi) overload in various pathophysiological states, an agent that selectively increases renal Pi excretion would be of major value. Previously, we have shown that dopamine (DA) inhibits Na(+)-Pi cotransport in renal epithelia. However, the administration of DA or its immediate precursor L-DOPA increases DA in multiple tissues. Synthetic dipeptide gamma-L-glutamyl-L-DOPA (gludopa) can serve as an inactive precursor (pro-pro-drug) of DA. This study tested the hypothesis that, because of the unique colocalization of gamma-glutamyltransferase (gamma-GT), aromatic amino acid decarboxylase, Na(+)-Pi cotransporter, and Na(+)-L-DOPA cotransporter in brush border membrane (BBM) of proximal tubular cells, gludopa may elicit phosphaturia by action of DA generated within the kidney. METHODS Thyroparathyrectomized rats were given placebo, or gludopa, or gludopa + gamma-GT inhibitor acivicin. Urinary excretion of Pi, Ca2+, Na+, K+, DA, cAMP, and cGMP was determined, and Na(+)-Pi cotransport was measured in BBM prepared from kidneys of rats at the end of the experiment. RESULTS The administration of gludopa resulted in: (a) an inhibition of Na(+)-Pi cotransport, but not cotransport of Na(+)-proline and Na(+)-alanine in BBM; (b) an increase (+300%) of fractional excretion (FE) of Pi and a drop (-35%) of plasma Pi, whereas the plasma levels and FEs of Ca2+, Na+, and K+ were unchanged; (c) an increase in urinary excretion of cAMP. but not cGMP; (d) a 1000-fold increase of urinary excretion of DA, without a change in excretion of norepinephrine; and (e) an incubation of gludopa with BBM in vitro, which caused a release of L-DOPA, and the in vivo administration of acivicin, which blocked actions of gludopa to inhibit Na(+)-Pi cotransport and to increase urinary excretions of Pi and DA. CONCLUSIONS We conclude that colocalization of enzymes of biotransformation, BBM transporters, and the autocrine/paracrine DA system in cells of proximal tubules constitutes a cellular basis for the potent and specific phosphaturic action of gludopa.
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Affiliation(s)
- F G de Toledo
- Department of Physiology and Biophysics, Mayo Clinic and Foundation, Mayo Medical School, Rochester, Minnesota, USA
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40
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Hussain T, Kansra V, Lokhandwala MF. Renal dopamine receptor signaling mechanisms in spontaneously hypertensive and Fischer 344 old rats. Clin Exp Hypertens 1999; 21:25-36. [PMID: 10052639 DOI: 10.3109/10641969909068646] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Dopamine plays an important role in the regulation of renal sodium excretion. The activation of D1-like receptors located on the proximal tubules causes inhibition of tubular sodium reabsorption by inhibiting Na,H-exchanger and Na,K-ATPase activity. The D1-like receptors are linked via G proteins to the multiple cellular signaling systems namely adenylyl cyclase and phospholipase C (PLC). A defective renal dopamine receptor function exists in spontaneously hypertensive rats (SHR). In the proximal tubules of SHR, the stimulation of adenylyl cyclase and PLC caused by dopamine was significantly reduced in comparison with Wistar-Kyoto (WKY) rats. Also unlike the effects seen in WKY, D1-like receptor activation did not inhibit Na,K-ATPase and Na,H-exchanger activities in SHR. In addition, reduced quantity of Gq/11alpha proteins was detected in the basolateral membranes of SHR compared to WKY rats. Studies revealed that there may be a primary defect in D1-like receptors leading to an altered signaling system in the proximal tubules and reduced dopamine-mediated effect on renal sodium excretion in SHR. Recently, it has been shown that the disruption of D1A receptors at the gene level causes hypertension in mice. Similar to SHR, dopamine and D1-like receptor agonist failed to inhibit Na,K-ATPase activity in the proximal tubules of old Fischer 344 rats. Unlike the observations in SHR where D1-like receptors were equal to WKY rats, there is a 50% decrease in D1-like receptor number in basolateral membranes of the old rats compared to the adult rats. Dopamine was unable to stimulate G proteins in the basolateral membranes of old rats compared to the adult rats. It is suggested that a defective dopamine receptors/signaling system may contribute to the development and maintenance of hypertension. Also, the inability of dopamine to inhibit Na,K-ATPase may lead to a reduced renal sodium excretion in response to dopamine in old rats.
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Affiliation(s)
- T Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, TX 77204-5511, USA
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41
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Hussain T, Abdul-Wahab R, Kotak DK, Lokhandwala MF. Bromocriptine regulates angiotensin II response on sodium pump in proximal tubules. Hypertension 1998; 32:1054-9. [PMID: 9856973 DOI: 10.1161/01.hyp.32.6.1054] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
-Dopamine and angiotensin II (Ang II) receptors have been reported to exhibit an interaction in renal proximal tubules. The present study was designed to investigate the regulation by a D2-like dopamine receptor of Ang II-mediated stimulation of Na,K-ATPase activity in the renal proximal tubules. Ang II (10(-13) to 10(-9) mol/L) stimulated Na,K-ATPase activity in the proximal tubules that was completely abolished when the tubules were pretreated with the D2-like receptor agonist bromocriptine (1 micromol/L) for 30 minutes. The effect of bromocriptine on Ang II response was prevented by domperidone (1 micromol/L), a D2-like dopamine receptor antagonist. Similarly, the inhibition of forskolin (1 micromol/L)-induced cAMP accumulation caused by Ang II (10 pmol/L) was also abolished in bromocriptine-pretreated tubules. Basal and forskolin-stimulated cAMP was not significantly different in bromocriptine-treated tubules compared with the control. [3H]-Ang II binding sites (angiotensin type 1 [AT1] receptors) were reduced by approximately 65% in bromocriptine-treated proximal tubules, a result that was further substantiated by Western blot analysis revealing a 50% decrease in AT1 receptors in bromocriptine-treated tubules compared with the control. Western blot analysis of G proteins revealed a 2-fold increase in Gsalpha and a 20% decrease in Gialpha1 and Gialpha2 in the bromocriptine-treated proximal tubules. Bromocriptine (1 micromol/L) alone stimulated Na,K-ATPase activity during the first 30 minutes of incubation, and thereafter the stimulation fell to the basal level. Similarly, bromocriptine-mediated inhibition of cAMP lasted only up to 20 minutes. The data suggest that preactivation of D2-like dopamine receptors abolishes Ang II-mediated stimulation of Na,K-ATPase activity and inhibition of cAMP accumulation. This phenomenon may be a consequence of a decrease in AT1 receptors and alterations in G protein levels in the proximal tubules. We propose that such a regulation of Ang II response by bromocriptine is the result of heterologous desensitization of the D2-like receptor system.
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Affiliation(s)
- T Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Houston, Tex 77204-5511, USA
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O'Connell DP, Vaughan CJ, Aherne AM, Botkin SJ, Wang ZQ, Felder RA, Carey RM. Expression of the dopamine D3 receptor protein in the rat kidney. Hypertension 1998; 32:886-95. [PMID: 9822449 DOI: 10.1161/01.hyp.32.5.886] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The dopamine D3 receptor subtype was identified in rat kidney using both light microscopic immunohistochemistry and electron microscopic immunocytochemistry. Antipeptide polyclonal antisera were directed to both extracellular and intracellular regions of the native D3 receptor. Selectivity of the antipeptide antisera was validated by their ability to recognize native receptor protein expressed in permanently transfected mouse LTK- cells or Spodoptera fragiperda (Sf9) cell membranes. Light microscopic immunohistochemical staining for the D3 receptor was observed only in the cortex. Specific staining was present in proximal and distal tubules, cortical collecting ducts, glomeruli, and renal vasculature. Immunostaining was observed predominantly in the apical portion of both the proximal and distal tubules. Renal arterial staining was prominent in the medial and adventitial layers. Electron microscopic immunocytochemistry revealed immunogold particles in arteriolar smooth muscle cells of the renal vasculature. In proximal and distal tubules and cortical collecting duct, immunogold staining was localized to apical portions of tubule cells. D3 receptor immunogold staining in the glomeruli was clearly present in podocytes. Western blot analysis demonstrated a single D3 receptor band in infected Sf9 cell membranes, in transfected LTK- cells, and in kidney and brain but not in noninfected Sf9 cell membranes or in D2 or D3 receptor transfected or nontransfected LTK- cells. The use of receptor subtype-selective antibodies allows for the tissue localization of specific dopamine receptors that are not distinguished by current pharmacological or ligand-binding technology. The rat kidney expresses the D3 receptor at sites previously deemed to have D2-like receptors.
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Affiliation(s)
- D P O'Connell
- Department of Pharmacology, University College Cork, Ireland
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43
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Abstract
During the past decade, it has become evident that dopamine plays an important role in the regulation of renal function and blood pressure. Dopamine exerts its actions via a class of cell-surface receptors coupled to G-proteins that belong to the rhodopsin family. Dopamine receptors have been classified into two families based on pharmacologic and molecular cloning studies. In mammals, two D1-like receptors that have been cloned, the D1 and D5 receptors (known as D1A and D1B, respectively, in rodents), are linked to stimulation of adenylyl cyclase. Three D2-like receptors that have been cloned (D2, D3, and D4) are linked to inhibition of adenylyl cyclase and Ca2+ channels and stimulation of K+ channels. All the mammalian dopamine receptors, initially cloned from the brain, have been found to be expressed outside the central nervous system, in such sites as the adrenal gland, blood vessels, carotid body, intestines, heart, parathyroid gland, and the kidney and urinary tract. Dopamine receptor subtypes are differentially expressed along the nephron, where they regulate renal hemodynamics and electrolyte and water transport, as well as renin secretion. The ability of renal proximal tubules to produce dopamine and the presence of receptors in these tubules suggest that dopamine can act in an autocrine or paracrine fashion; this action becomes most evident during extracellular fluid volume expansion. This renal autocrine/paracrine function is lost in essential hypertension and in some animal models of genetic hypertension; disruption of the D1 or D3 receptor produces hypertension in mice. In humans with essential hypertension, renal dopamine production in response to sodium loading is often impaired and may contribute to the hypertension. The molecular basis for the dopaminergic dysfunction in hypertension is not known, but may involve an abnormal post-translational modification of the dopamine receptor.
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Affiliation(s)
- P A Jose
- Department of Pediatrics, Georgetown University Medical Center, Washington, DC 20007, USA
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44
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Nussenzveig DR, Matos MD, Thaw CN. Human calcitonin receptor is directly targeted to and retained in the basolateral surface of MDCK cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C1264-76. [PMID: 9814975 DOI: 10.1152/ajpcell.1998.275.5.c1264] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The human calcitonin receptor (hCTR) is expressed in polarized cells of the kidney, bone, and nervous system. In the kidney, hCTRs are found in cells of the distal nephron to which blood-borne calcitonin has access only at the basolateral surface. We expressed hCTR subtypes 1 and 2 in Madin-Darby canine kidney (MDCK) cells to establish a cell model useful for delineating the molecular mechanisms underlying hCTR polarity. Selective cell surface incubation demonstrated functional polarity of hCTRs by equilibrium binding or cross-linking of radioiodinated salmon calcitonin (125I-sCT) and cAMP accumulation stimulated by sCT. We estimated that at the steady state there are 40-fold more hCTRs on the basolateral than on the apical side. Domain-selective cell surface biotinylation followed by immunoblotting of streptavidin-agarose-fractionated biotinylated glycoproteins independently confirmed the polarized distribution of FLAG epitope-tagged hCTR-2 in the basolateral domain. Confocal microscopy of immunostained receptors revealed that hCTRs are concentrated on a lateral subdomain of the basolateral membrane. Cell surface arrival assay of newly formed receptors demonstrated that direct delivery to the basolateral domain is the mechanism by which hCTRs become polarized. Measurement of receptor turnover on the basolateral surface showed that retention contributes to hCTR distribution at the steady state.
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Affiliation(s)
- D R Nussenzveig
- Division of Molecular Medicine, Department of Medicine, Cornell University Medical College, New York, New York 10021, USA
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45
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Abstract
BACKGROUND Dopamine can produce a natriuresis and diuresis independent of changes in renal hemodynamics. However, previous studies have failed to demonstrate an inhibition of transport by dopamine in intact proximal convoluted tubules. METHODS Rabbit proximal convoluted tubules were perfused in vitro with an ultrafiltrate-like solution and bathed in a serum-like albumin solution. RESULTS In the present study, the addition of 10-5 M dopamine to the lumen or bath of proximal convoluted tubules perfused in vitro had no effect on transport. In proximal convoluted tubules, addition of 10-6 M bath norepinephrine increased the rate of volume absorption from 0.65 +/- 0.08 to 0.93 +/- 0.08 nl/mm. min (P < 0.01). Addition of 10-5 M luminal dopamine in the presence of bath norepinephrine inhibited the rate of volume absorption to 0.72 +/- 0.10 nl/mm. min (P = 0.01). The inhibition in the rate of volume absorption by luminal dopamine in the presence of bath norepinephrine was completely blocked by the DA1 antagonist, SCH 23390. The DA1 agonist luminal 10-5 M fenoldopam also inhibited volume absorption in the presence of bath norepinephrine, but the DA2 agonist luminal 10-5 M quinpirole was without effect. Bath 10-5 M dopamine had no effect on volume absorption in the presence of bath norepinephrine. CONCLUSION Dopamine has no direct epithelial action on the proximal convoluted tubule. However, luminal dopamine antagonizes the stimulation in transport produced by norepinephrine. These studies suggest that luminal dopamine may play a role to modulate sodium transport in the presence of renal nerve activity.
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Affiliation(s)
- M Baum
- Departments of Pediatrics and Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
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46
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LeClaire MM, Berndt TJ, Knox FG. Effect of renal interstitial infusion of L-dopa on sodium and phosphate excretions. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 1998; 132:308-12. [PMID: 9794702 DOI: 10.1016/s0022-2143(98)90044-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It has been hypothesized that dopamine synthesized by the proximal tubule can act as a paracrine substance that regulates reabsorption by the proximal tubule. The present study was performed to study the effects of the stimulation of endogenous synthesis of dopamine by infusion of L-DOPA directly into the renal interstitium on sodium and phosphate excretions and to determine the roles of D1 and D2 receptors in the response. The infusion of L-DOPA (50 microg/kg/min) into the renal interstitium through an implanted matrix significantly increased the fractional excretion of sodium (FENa) from 1.0%+/-0.2% to 3.1%+/-0.6% and the fractional excretion of phosphate (FEPi) from 23%+/-3% to 36%+/-3%, P < .05, n = 10. The infusion of D1 receptor antagonist SCH23390 or SKF83566 (5 microg/kg/min) into the renal interstitium blocked the natriuretic (FENa 1.5%+/-0.2% to 1.9%+/-0.4%) and phosphaturic (FEPi 41%+/-3% to 41%+/-4%) effects of L-DOPA infusion. The infusion of the D2 receptor antagonist sulpiride at a rate of 4 microg/kg/min into the renal interstitium also attenuated the natriuretic (FENa 1.3%+/-0.3% to 1.6%+/-0.5%) and phosphaturic effects of L-DOPA infusion (FEPi 36%+/-5% to 39%+/-5%). We conclude that the renal interstitial infusion of L-DOPA increases sodium and phosphate excretions and that these responses are mediated by D1 and D2 receptors.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/analogs & derivatives
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Benzazepines/pharmacology
- Dopamine/biosynthesis
- Dopamine Agents/pharmacology
- Dopamine Antagonists/pharmacology
- Dopamine D2 Receptor Antagonists
- Infusions, Parenteral
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Levodopa/pharmacology
- Male
- Natriuresis/drug effects
- Phosphates/urine
- Rats
- Rats, Sprague-Dawley
- Receptors, Dopamine D1/antagonists & inhibitors
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/metabolism
- Sodium/urine
- Sulpiride/pharmacology
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Affiliation(s)
- M M LeClaire
- Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA
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47
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Abstract
Dopamine plays an important role in the regulation of renal sodium excretion. The synthesis of dopamine and the presence of dopamine receptor subtypes (D1A, D1B, as D1-like and D2, and D3 as D2-like) have been shown within the kidney. The activation of D1-like receptors located on the proximal tubules causes inhibition of tubular sodium reabsorption by inhibiting Na,H-exchanger and Na,K-ATPase activity. The D1-like receptors are linked to the multiple cellular signaling systems (namely, adenylyl cyclase, phospholipase C, and phospholipase A2) in the different regions of the nephron. Defective renal dopamine production and/or dopamine receptor function have been reported in human primary hypertension as well as in genetic models of animal hypertension. There may be a primary defect in D1-like receptors and an altered signaling system in the proximal tubules that lead to reduced dopamine-mediated effects on renal sodium excretion in hypertension. Recently, it has been shown in animal models that the disruption of either D1A or D3 receptors at the gene level causes hypertension in mice. Dopamine and dopamine receptor agonists also provide therapeutic potential in treatment of various cardiovascular pathological conditions, including hypertension. However, because of the poor bioavailability of the currently available compounds, the use of D1-like agonists is limited to the management of patients with severe hypertension when a rapid reduction of blood pressure is clinically indicated and in acute management of patients with heart failure. In conclusion, there is convincing evidence that dopamine and dopamine receptors play an important role in regulation of renal function, suggesting that a defective dopamine receptor/signaling system may contribute to the development and maintenance of hypertension. Further studies need to be directed toward establishing a direct correlation between defective dopamine receptor gene in the kidney and development of hypertension. Subsequently, it may be possible to use a therapeutic approach to correct the defect in dopamine receptor gene causing the hypertension.
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Affiliation(s)
- T Hussain
- Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Texas 77204-5511, USA
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48
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Chibalin AV, Zierath JR, Katz AI, Berggren PO, Bertorello AM. Phosphatidylinositol 3-kinase-mediated endocytosis of renal Na+, K+-ATPase alpha subunit in response to dopamine. Mol Biol Cell 1998; 9:1209-20. [PMID: 9571250 PMCID: PMC25342 DOI: 10.1091/mbc.9.5.1209] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Dopamine (DA) inhibition of Na+,K+-ATPase in proximal tubule cells is associated with increased endocytosis of its alpha and beta subunits into early and late endosomes via a clathrin vesicle-dependent pathway. In this report we evaluated intracellular signals that could trigger this mechanism, specifically the role of phosphatidylinositol 3-kinase (PI 3-K), the activation of which initiates vesicular trafficking and targeting of proteins to specific cell compartments. DA stimulated PI 3-K activity in a time- and dose-dependent manner, and this effect was markedly blunted by wortmannin and LY 294002. Endocytosis of the Na+,K+-ATPase alpha subunit in response to DA was also inhibited in dose-dependent manner by wortmannin and LY 294002. Activation of PI 3-K generally occurs by association with tyrosine kinase receptors. However, in this study immunoprecipitation with a phosphotyrosine antibody did not reveal PI 3-K activity. DA-stimulated endocytosis of Na+, K+-ATPase alpha subunits required protein kinase C, and the ability of DA to stimulate PI 3-K was blocked by specific protein kinase C inhibitors. Activation of PI 3-K is mediated via the D1 receptor subtype and the sequential activation of phospholipase A2, arachidonic acid, and protein kinase C. The results indicate a key role for activation of PI 3-K in the endocytic sequence that leads to internalization of Na+,K+-ATPase alpha subunits in response to DA, and suggest a mechanism for the participation of protein kinase C in this process.
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Affiliation(s)
- A V Chibalin
- Department of Molecular Medicine, Karolinska Institute, Karolinska Hospital, 171 76 Stockholm, Sweden
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49
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Edwards RM, Trizna W, Stack EJ. [125I]endothelin-1 binding to renal brush border and basolateral membranes. Eur J Pharmacol 1998; 345:229-32. [PMID: 9600642 DOI: 10.1016/s0014-2999(98)00090-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
[125I]Endothelin-1 bound with high affinity to a single site on both brush border membranes (Kd=192+/-26 pM. Bmax=314+/-49 fmol/mg) and basolateral membranes (Kd=94.7+/-3.4 pM, Bmax=612+/-107 fmol/mg) isolated from rat renal cortex. Competition binding experiments using subtype selective ligands revealed that the proportion of ET(B) to ET(A) receptors was 80:20 and 60:40 in the brush border membrane and the basolateral membrane, respectively. The results demonstrate that endothelin-1 binds to brush border membranes, and that endothelin ET(B) receptors may be involved in the previously described effects of endothelin-1 on brush border membrane Na+ transport.
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Affiliation(s)
- R M Edwards
- Department of Renal Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406-0939, USA
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50
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Missale C, Nash SR, Robinson SW, Jaber M, Caron MG. Dopamine receptors: from structure to function. Physiol Rev 1998; 78:189-225. [PMID: 9457173 DOI: 10.1152/physrev.1998.78.1.189] [Citation(s) in RCA: 2416] [Impact Index Per Article: 92.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The diverse physiological actions of dopamine are mediated by at least five distinct G protein-coupled receptor subtypes. Two D1-like receptor subtypes (D1 and D5) couple to the G protein Gs and activate adenylyl cyclase. The other receptor subtypes belong to the D2-like subfamily (D2, D3, and D4) and are prototypic of G protein-coupled receptors that inhibit adenylyl cyclase and activate K+ channels. The genes for the D1 and D5 receptors are intronless, but pseudogenes of the D5 exist. The D2 and D3 receptors vary in certain tissues and species as a result of alternative splicing, and the human D4 receptor gene exhibits extensive polymorphic variation. In the central nervous system, dopamine receptors are widely expressed because they are involved in the control of locomotion, cognition, emotion, and affect as well as neuroendocrine secretion. In the periphery, dopamine receptors are present more prominently in kidney, vasculature, and pituitary, where they affect mainly sodium homeostasis, vascular tone, and hormone secretion. Numerous genetic linkage analysis studies have failed so far to reveal unequivocal evidence for the involvement of one of these receptors in the etiology of various central nervous system disorders. However, targeted deletion of several of these dopamine receptor genes in mice should provide valuable information about their physiological functions.
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Affiliation(s)
- C Missale
- Department of Cell Biology, Howard Hughes Medical Institute Laboratories, Duke University Medical Center, Durham, North Carolina, USA
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