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Wang Y, LaRocque LM, Ruiz JA, Rodriguez EL, Sands JM, Klein JD. Aldosterone Contributes to Vasopressin Escape through Changes in Water and Urea Transport. Biomedicines 2023; 11:1844. [PMID: 37509484 PMCID: PMC10376660 DOI: 10.3390/biomedicines11071844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/20/2023] [Accepted: 06/22/2023] [Indexed: 07/30/2023] Open
Abstract
Hyponatremia (hypo-osmolality) is a disorder of water homeostasis due to abnormal renal diluting capacity. The body limits the degree to which serum sodium concentration falls through a mechanism called "vasopressin escape". Vasopressin escape is a process that prevents the continuous decrease in serum sodium concentration even under conditions of sustained high plasma vasopressin levels. Previous reports suggest that aldosterone may be involved in the vasopressin escape mechanism. The abilities of aldosterone synthase (Cyp11b2) knockout and wild-type mice to escape from vasopressin were compared. Wild-type mice escaped while the aldosterone synthase knockout mice did not. Both the water channel aquaporin 2 (AQP2) and the urea transporter UT-A1 protein abundances were higher in aldosterone synthase knockout than in wild-type mice at the end of the escape period. Vasopressin escape was also blunted in rats given spironolactone, a mineralocorticoid receptor blocker. Next, the role of the phosphatase, calcineurin (protein phosphatase 2B, PP2B), in vasopressin escape was studied since aldosterone activates calcineurin in rat cortical collecting ducts. Tacrolimus, a calcineurin inhibitor, blunted vasopressin escape in rats compared with the control rats, increased UT-A1, AQP2, and pS256-AQP2, and decreased pS261-AQP2 protein abundances. Our results indicate that aldosterone regulates vasopressin escape through calcineurin-mediated protein changes in UT-A1 and AQP2.
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Affiliation(s)
- Yanhua Wang
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Lauren M LaRocque
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Joseph A Ruiz
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Eva L Rodriguez
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Jeff M Sands
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
| | - Janet D Klein
- Renal Division, Department of Medicine, Emory University, Atlanta, GA 30322, USA
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2
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Wang Y, Klein JD, Sands JM. Phosphatases Decrease Water and Urea Permeability in Rat Inner Medullary Collecting Ducts. Int J Mol Sci 2023; 24:ijms24076537. [PMID: 37047509 PMCID: PMC10095045 DOI: 10.3390/ijms24076537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 03/27/2023] [Accepted: 03/29/2023] [Indexed: 04/03/2023] Open
Abstract
We previously showed that the phosphatases PP1/PP2A and PP2B dephosphorylate the water channel, AQP2, suggesting their role in water reabsorption. In this study, we investigated whether protein phosphatase 2A (PP2A) and protein phosphatase 2B (PP2B or calcineurin), which are present in the inner medullary collecting duct (IMCD), are regulators of urea and water permeability. Inhibition of calcineurin by tacrolimus increased both basal and vasopressin-stimulated osmotic water permeability in perfused rat IMCDs. However, tacrolimus did not affect osmotic water permeability in the presence of aldosterone. Inhibition of PP2A by calyculin increased both basal and vasopressin-stimulated osmotic water permeability, and aldosterone reversed the increase by calyculin. Previous studies showed that adrenomedullin (ADM) activates PP2A and decreases osmotic water permeability. Inhibition of PP2A by calyculin prevented the ADM-induced decrease in water reabsorption. ADM reduced the phosphorylation of AQP2 at serine 269 (pSer269 AQP2). Urea is linked to water reabsorption by building up hyperosmolality in the inner medullary interstitium. Calyculin increased urea permeability and phosphorylated UT-A1. Our results indicate that phosphatases regulate water reabsorption. Aldosterone and adrenomedullin decrease urea or osmotic water permeability by acting through calcineurin and PP2A, respectively. PP2A may regulate water reabsorption by dephosphorylating pSer269, AQP2, and UT-A1.
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Jo R, Shibata H, Kurihara I, Yokota K, Kobayashi S, Murai-Takeda A, Mitsuishi Y, Hayashi T, Nakamura T, Itoh H. Mechanisms of mineralocorticoid receptor-associated hypertension in diabetes mellitus: the role of O-GlcNAc modification. Hypertens Res 2023; 46:19-31. [PMID: 36229526 DOI: 10.1038/s41440-022-01036-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 09/04/2022] [Accepted: 09/05/2022] [Indexed: 02/03/2023]
Abstract
This study investigated the mechanism underlying the beneficial effects of mineralocorticoid receptor (MR) antagonists in patients with resistant hypertension and diabetic nephropathy by examining post-translational modification of the MR by O-linked-N-acetylglucosamine (O-GlcNAc), which is strongly associated with type 2 diabetes. Coimmunoprecipitation assays in HEK293T cells showed that MR is a target of O-GlcNAc modification (O-GlcNAcylation). The expression levels and transcriptional activities of the receptor increased in parallel with its O-GlcNAcylation under high-glucose conditions. Liquid chromatography-tandem mass spectrometry revealed O-GlcNAcylation of the MR at amino acids 295-307. Point mutations in those residues decreased O-GlcNAcylation, and both the protein levels and transcriptional activities of MR. In db/db mouse kidneys, MR protein levels increased in parallel with overall O-GlcNAc levels of the tissue, accompanied by increased SGK1 mRNA levels. The administration of 6-diazo-5-oxo-L-norleucin, an inhibitor of O-GlcNAcylation, reduced tissue O-GlcNAc levels and MR protein levels in db/db mice. Thus, our study showed that O-GlcNAcylation of the MR directly increases protein levels and transcriptional activities of the receptor under high-glucose conditions in vitro and in vivo. These findings provide a novel mechanism of MR as a target for prevention of complications associated with diabetes mellitus.
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Affiliation(s)
- Rie Jo
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Keiyu Hospital, Kanagawa, Japan
| | - Hirotaka Shibata
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan. .,Department of Endocrinology, Metabolism, Rheumatology and Nephrology, Faculty of Medicine, Oita University, Oita, Japan.
| | - Isao Kurihara
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Department of Medical Education, National Defense Medical College, Saitama, Japan
| | - Kenichi Yokota
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Division of Metabolism and Endocrinology, Department of Internal Medicine, St. Marianna University School of Medicine, Kanagawa, Japan
| | - Sakiko Kobayashi
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Ayano Murai-Takeda
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Health Center, Keio University, Kanagawa, Japan
| | - Yuko Mitsuishi
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Center of Preventive Medicine, Keio University Hospital, Tokyo, Japan
| | - Takeshi Hayashi
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.,Hayashi Clinic, Tokyo, Japan
| | - Toshifumi Nakamura
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
| | - Hiroshi Itoh
- Division of Endocrinology, Metabolism and Nephrology, Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan
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Wang Y, Ma F, Rodriguez EL, Klein JD, Sands JM. Aldosterone Decreases Vasopressin-Stimulated Water Reabsorption in Rat Inner Medullary Collecting Ducts. Cells 2020; 9:cells9040967. [PMID: 32295252 PMCID: PMC7226978 DOI: 10.3390/cells9040967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 04/09/2020] [Accepted: 04/10/2020] [Indexed: 11/27/2022] Open
Abstract
Aldosterone indirectly regulates water reabsorption in the distal tubule by regulating sodium reabsorption. However, the direct effect of aldosterone on vasopressin-regulated water and urea permeability in the rat inner medullary collecting duct (IMCD) has not been tested. We investigated whether aldosterone regulates osmotic water permeability in isolated perfused rat IMCDs. Adding aldosterone (500 nM) to the bath significantly decreased osmotic water permeability in the presence of vasopressin (50 pM) in both male and female rat IMCDs. Aldosterone significantly decreased aquaporin-2 (AQP2) phosphorylation at S256 but did not change it at S261. Previous studies show that aldosterone can act both genomically and non-genomically. We tested the mechanism by which aldosterone attenuates osmotic water permeability. Blockade of gene transcription with actinomycin D did not reverse aldosterone-attenuated osmotic water permeability. In addition to AQP2, the urea transporter UT-A1 contributes to vasopressin-regulated urine concentrating ability. We tested aldosterone-regulated urea permeability in vasopressin-treated IMCDs. Blockade of gene transcription did not reverse aldosterone-attenuated urea permeability. In conclusion, aldosterone directly regulates water reabsorption through a non-genomic mechanism. Aldosterone-attenuated water reabsorption may be related to decreased trafficking of AQP2 to the plasma membrane. There may be a sex difference apparent in the inhibitory effect of aldosterone on water reabsorption in the inner medullary collecting duct. This study is the first to show a direct effect of aldosterone to inhibit vasopressin-stimulated osmotic water permeability and urea permeability in perfused rat IMCDs.
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Affiliation(s)
| | | | | | | | - Jeff M. Sands
- Correspondence: ; Tel.: +1-404-7272-525; Fax: +1-404-7273-425
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Leite-Dellova DCA, Szriber SJ, Merighe GKF, Polidoro JZ, Rebouças NA, Oliveira-Souza M, de Mello-Aires M. Signaling pathways involved in the rapid biphasic effect of aldosterone on Na +/H + exchanger in rat proximal tubule cells. J Steroid Biochem Mol Biol 2018; 182:87-94. [PMID: 29702262 DOI: 10.1016/j.jsbmb.2018.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 04/21/2018] [Accepted: 04/23/2018] [Indexed: 10/17/2022]
Abstract
The receptors and signaling pathways for nongenomic effects of aldosterone (Aldo) on the proximal Na+/H+ exchanger are still unknown; therefore, the aim of this study was to investigate the mineralocorticoid receptor (MR) and/or glucocorticoid receptor (GR) participation in rapid Aldo effects on NHE1 (basolateral Na+/H+ exchanger isoform) and cytosolic calcium concentration ([Ca2+]i). In addition, phospholipase C (PLC), protein kinase C (PKC), and mitogen-activated protein kinase kinase (MEK) involvement in signaling pathways of such effects was evaluated, using immortalized proximal tubule cells of rat (IRPTC) as an experimental model. MR and GR expression was investigated using reverse transcription polymerase chain reaction and immunoblotting. The intracellular pH recovery rate (after acid loading) and [Ca2+]i were determined by the probes BCECF-AM and FURA 2-AM, respectively. Aldo (10-12 M) promoted a moderate increase in [Ca2+]i and stimulation of NHE1, whereas Aldo (10-6 M) greatly increased the [Ca2+]i, but inhibited the NHE1. BAPTA-AM (a calcium chelator), GR antagonism and inhibition of PLC, PKC and MEK pathway abolished the biphasic and dose-dependent effect of Aldo on NHE1 and decreased the [Ca2+]i; whereas MR do not appear to participate in this rapid signaling in IRPTC cells. The reduction of GR content, by gene silencing, abolished the Aldo effect on NHE1, in low concentration, confirming the importance of this receptor in the rapid modulation of proximal sodium and hydrogen transports.
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Affiliation(s)
- Deise C A Leite-Dellova
- Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of Sao Paulo, Pirassununga, Brazil.
| | - Shirley J Szriber
- Department of Veterinary Medicine, Faculty of Animal Science and Food Engineering, University of Sao Paulo, Pirassununga, Brazil
| | - Giovana K F Merighe
- Basic Sciences, Faculty of Animal Science and Food Engineering, University of Sao Paulo, Pirassununga, Brazil
| | - Juliano Z Polidoro
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Nancy A Rebouças
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Maria Oliveira-Souza
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
| | - Margarida de Mello-Aires
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, Brazil
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6
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Bell SG. Minding the Gap: Utility of the Anion Gap in the Differential Diagnosis of Metabolic Acidosis. Neonatal Netw 2017; 36:229-232. [PMID: 28764826 DOI: 10.1891/0730-0832.36.4.229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The anion gap, in conjunction with other laboratory results, can be a useful clue in the differential diagnosis of metabolic acidosis. There are three primary causes of metabolic acidosis: loss of base, decreased renal excretion of acid, and increased acid production. Depending on the cause of metabolic acidosis, the anion gap may be elevated or normal.
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Abstract
The H(+) concentration in human blood is kept within very narrow limits, ~40 nmol/L, despite the fact that dietary metabolism generates acid and base loads that are added to the systemic circulation throughout the life of mammals. One of the primary functions of the kidney is to maintain the constancy of systemic acid-base chemistry. The kidney has evolved the capacity to regulate blood acidity by performing three key functions: (i) reabsorb HCO3(-) that is filtered through the glomeruli to prevent its excretion in the urine; (ii) generate a sufficient quantity of new HCO3(-) to compensate for the loss of HCO3(-) resulting from dietary metabolic H(+) loads and loss of HCO3(-) in the urea cycle; and (iii) excrete HCO3(-) (or metabolizable organic anions) following a systemic base load. The ability of the kidney to perform these functions requires that various cell types throughout the nephron respond to changes in acid-base chemistry by modulating specific ion transport and/or metabolic processes in a coordinated fashion such that the urine and renal vein chemistry is altered appropriately. The purpose of the article is to provide the interested reader with a broad review of a field that began historically ~60 years ago with whole animal studies, and has evolved to where we are currently addressing questions related to kidney acid-base regulation at the single protein structure/function level.
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Affiliation(s)
- Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, Los Angeles, CA; Brain Research Institute, UCLA, Los Angeles, CA
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8
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Abstract
The proximal tubule reabsorbs most of the filtered bicarbonate which is mediated in large part by Na+/H+ exchange (NHE). We have previously demonstrated that there is an isoform switch during postnatal maturation from NHE8 to NHE3 that is concordant with the postnatal increase in serum glucocorticoid levels. To examine if glucocorticoids may be responsible for this isoform switch, we administered dexamethasone daily to mice at 7–10 days of age, a time prior to the normal isoform switch. We show that compared to vehicle-treated controls, dexamethasone caused a premature increase in renal NHE3 and decrease in NHE8 mRNA, total protein, and brush border membrane protein abundance. To examine if there was a direct epithelial action of dexamethasone on NHE8, we studied normal rat kidney (NRK) cells in vitro which express NHE8 on their apical membrane. Dexamethasone decreased NHE8 mRNA, total protein, and apical protein abundance. Dexamethasone also decreased Na+/H+ exchanger activity. These studies provide evidence that glucocorticoids may play a role in the developmental isoform switch from NHE8 to NHE3 and cause a decrease in NHE8 expression and activity.
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Affiliation(s)
- Catherine Joseph
- Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas Dallas, Texas 75235-9063
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Salyer SA, Parks J, Barati MT, Lederer ED, Clark BJ, Klein JD, Khundmiri SJ. Aldosterone regulates Na(+), K(+) ATPase activity in human renal proximal tubule cells through mineralocorticoid receptor. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2143-52. [PMID: 23684706 DOI: 10.1016/j.bbamcr.2013.05.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 04/15/2013] [Accepted: 05/08/2013] [Indexed: 12/21/2022]
Abstract
The mechanisms by which aldosterone increases Na(+), K(+) ATPase and sodium channel activity in cortical collecting duct and distal nephron have been extensively studied. Recent investigations demonstrate that aldosterone increases Na-H exchanger-3 (NHE-3) activity, bicarbonate transport, and H(+) ATPase in proximal tubules. However, the role of aldosterone in regulation of Na(+), K(+) ATPase in proximal tubules is unknown. We hypothesize that aldosterone increases Na(+), K(+) ATPase activity in proximal tubules through activation of the mineralocorticoid receptor (MR). Immunohistochemistry of kidney sections from human, rat, and mouse kidneys revealed that the MR is expressed in the cytosol of tubules staining positively for Lotus tetragonolobus agglutinin and type IIa sodium-phosphate cotransporter (NpT2a), confirming proximal tubule localization. Adrenalectomy in Sprague-Dawley rats decreased expression of MR, ENaC α, Na(+), K(+) ATPase α1, and NHE-1 in all tubules, while supplementation with aldosterone restored expression of above proteins. In human kidney proximal tubule (HKC11) cells, treatment with aldosterone resulted in translocation of MR to the nucleus and phosphorylation of SGK-1. Treatment with aldosterone also increased Na(+), K(+) ATPase-mediated (86)Rb uptake and expression of Na(+), K(+) ATPase α1 subunits in HKC11 cells. The effects of aldosterone on Na(+), K(+) ATPase-mediated (86)Rb uptake were prevented by spironolactone, a competitive inhibitor of aldosterone for the MR, and partially by Mifepristone, a glucocorticoid receptor (GR) inhibitor. These results suggest that aldosterone regulates Na(+), K(+) ATPase in renal proximal tubule cells through an MR-dependent mechanism.
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Affiliation(s)
- Sarah A Salyer
- Department of Medicine, Kidney Disease Program, University of Louisville, Louisville, KY, USA
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Braga-Sobrinho C, Leite-Dellova DCA, Mello-Aires M. Action of ANP on the nongenomic dose-dependent biphasic effect of aldosterone on NHE1 in proximal S3 segment. J Steroid Biochem Mol Biol 2012; 128:89-97. [PMID: 22154810 DOI: 10.1016/j.jsbmb.2011.11.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 11/18/2011] [Accepted: 11/19/2011] [Indexed: 10/15/2022]
Abstract
The rapid (2 min) nongenomic effects of aldosterone (ALDO) and/or spironolactone (MR antagonist), RU 486 (GR antagonist), atrial natriuretic peptide (ANP) and dimethyl-BAPTA (BAPTA) on the intracellular pH recovery rate (pHirr) via NHE1 (basolateral Na⁺/H⁺ exchanger isoform), after the acid load induced by NH₄Cl, and on the cytosolic free calcium concentration ([Ca²⁺](i)) were investigated in the proximal S3 segment isolated from rats, by the probes BCECF-AM and FLUO-4-AM, respectively. The basal pHi was 7.15±0.008 and the basal pHirr was 0.195±0.012 pH units/min (number of tubules/number of tubular areas=16/96). Our results confirmed the rapid biphasic effect of ALDO on NHE1: ALDO (10⁻¹² M) increases the pHirr to approximately 59% of control value, and ALDO (10⁻⁶ M) decreases it to approximately 49%. Spironolactone did not change these effects, but RU 486 inhibited the stimulatory effect and maintained the inhibitory effect. ANP (10⁻⁶ M) or BAPTA (5×10⁻⁵ M) alone had no significant effect on NHE1 but prevented both effects of ALDO on this exchanger. The basal [Ca²⁺](i) was 104±3 nM (15), and ALDO (10⁻¹² or 10⁻⁶ M) increased the basal [Ca²⁺](i) to approximately 50% or 124%, respectively. RU 486, ANP and BAPTA decreased the [Ca²⁺](i) and inhibited the stimulatory effect of both doses of ALDO. The results suggest the involvement of GR on the nongenomic effects of ALDO and indicate a pHirr-regulating role for [Ca²⁺](i) that is mediated by NHE1, stimulated/impaired by ALDO, and affected by ANP or BAPTA with ALDO. The observed nongenomic hormonal interaction in the S3 segment may represent a rapid and physiologically relevant regulatory mechanism in the intact animal under conditions of volume alterations.
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Affiliation(s)
- C Braga-Sobrinho
- Department of Physiology and Biophysics, Instituto de Ciências Biomédicas, University of São Paulo, Av. Prof. Lineu Prestes, 1524, Cidade Universitária, 05508-900 SP, Brazil
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Leite-Dellova DCA, Malnic G, Mello-Aires M. Genomic and nongenomic stimulatory effect of aldosterone on H+-ATPase in proximal S3 segments. Am J Physiol Renal Physiol 2010; 300:F682-91. [PMID: 21190948 DOI: 10.1152/ajprenal.00172.2010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The genomic and nongenomic effects of aldosterone on the intracellular pH recovery rate (pHirr) via H(+)-ATPase and on cytosolic free calcium concentration ([Ca(2+)](i)) were investigated in isolated proximal S3 segments of rats during superfusion with an Na(+)-free solution, by using the fluorescent probes BCECF-AM and FLUO-4-AM, respectively. The pHirr, after cellular acidification with a NH(4)Cl pulse, was 0.064 ± 0.003 pH units/min (n = 17/74) and was abolished with concanamycin. Aldosterone (10(-12), 10(-10), 10(-8), or 10(-6) M with 1-h or 15- or 2-min preincubation) increased the pHirr. The baseline [Ca(2+)](i) was 103 ± 2 nM (n = 58). After 1 min of aldosterone preincubation, there was a transient and dose-dependent increase in [Ca(2+)](i) and after 6-min preincubation there was a new increase in [Ca(2+)](i) that persisted after 1 h. Spironolactone [mineralocorticoid (MR) antagonist], actinomycin D, or cycloheximide did not affect the effects of aldosterone (15- or 2-min preincubation) on pHirr and on [Ca(2+)](i) but inhibited the effects of aldosterone (1-h preincubation) on these parameters. RU 486 [glucocorticoid (GR) antagonist] and dimethyl-BAPTA (Ca(2+) chelator) prevented the effect of aldosterone on both parameters. The data indicate a genomic (1 h, via MR) and a nongenomic action (15 or 2 min, probably via GR) on the H(+)-ATPase and on [Ca(2+)](i). The results are compatible with stimulation of the H(+)-ATPase by increases in [Ca(2+)](i) (at 10(-12)-10(-6) M aldosterone) and inhibition of the H(+)-ATPase by decreases in [Ca(2+)](i) (at 10(-12) or 10(-6) M aldosterone plus RU 486).
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Affiliation(s)
- D C A Leite-Dellova
- Department of Basic Sciences, Faculdade de Zootecnia e Engenharia de Alimentos, Campus of Pirassununga, Instituto de Ciências Biomédicas, University of São Paulo, São Paulo, Brazil
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