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Expression of phosphate and calcium transporters and their regulators in parotid glands of mice. Pflugers Arch 2023; 475:203-216. [PMID: 36274099 PMCID: PMC9849193 DOI: 10.1007/s00424-022-02764-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/07/2022] [Accepted: 10/13/2022] [Indexed: 02/01/2023]
Abstract
The concentration of inorganic phosphate (Pi) in plasma is under hormonal control, with deviations from normal values promptly corrected to avoid hyper- or hypophosphatemia. Major regulators include parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23), and active vitamin D3 (calcitriol). This control is achieved by mechanisms largely dependent on regulating intestinal absorption and renal excretion, whose combined actions stabilise plasma Pi levels at around 1-2 mM. Instead, Pi concentrations up to 13 and 40 mM have been measured in saliva from humans and ruminants, respectively, suggesting that salivary glands have the capacity to concentrate Pi. Here we analysed the transcriptome of parotid glands, ileum, and kidneys of mice, to investigate their potential differences regarding the expression of genes responsible for epithelial transport of Pi as well as their known regulators. Given that Pi and Ca2+ homeostasis are tightly connected, the expression of genes involved in Ca2+ homeostasis was also included. In addition, we studied the effect of vitamin D3 treatment on the expression of Pi and Ca2+ regulating genes in the three major salivary glands. We found that parotid glands are equipped preferentially with Slc20 rather than with Slc34 Na+/Pi cotransporters, are suited to transport Ca2+ through the transcellular and paracellular route and are potential targets for PTH and vitamin D3 regulation.
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2
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The kinetics of inorganic phosphate excretion in the acidotic rabbit during intravenous phosphate loading: a pseudo-ruminant model. Sci Rep 2020; 10:3988. [PMID: 32132645 PMCID: PMC7055221 DOI: 10.1038/s41598-020-61069-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 02/17/2020] [Indexed: 11/17/2022] Open
Abstract
The rabbit is a much-used experimental animal in renal tubule physiology studies. Although a monogastric mammal, the rabbit is a known hindgut fermenter. That ruminant species excrete inorganic phosphate (Pi) mainly through the digestive system while non-ruminants eliminate surplus phosphate primarily through the renal system are acknowledged facts. To understand phosphate homeostasis in the acidotic rabbit, anaesthetized animals were infused with hydrochloric acid, after which they underwent intravenous phosphate loading. Biofluids were collected during the infusion process for analysis. Plasma Pi increased (7.9 ± 1.7 mmoles.Litre−1 (N = 5) vs 2.2 ± 0.4 mmoles.Litre−1 (N = 10) pre-infusion, (p < 0.001)), while urinary phosphate excretion was also enhanced (74.4 ± 15.3 from a control value of 4.7 ± 3 µmol.min−1 (N = 9), pre-infusion, p < 0.001)) over an 82.5 minute Pi loading period. However, the fractional excretion of Pi (FePi) only increased from 14.2 ± 5.4% to a maximum of 61.7 ± 19% (N = 5) over the infusion period. Furthermore, the renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmPi/GFR) computed to 3.5 mmol.L−1, while a reading of 23.2 µmol.min−1.Kg.0.75 was obtained for the transport maximum for Pi (TmPi). The high reabsorptivity of the rabbit nephrons coupled with possibly a high secretory capacity of the salivary glands for Pi, may constitute a unique physiological mechanism that ensures the rabbit hindgut receives adequate phosphate to regulate caecal pH in favour of the resident metabolically - active microbiota. The handling of Pi by the rabbit is in keeping with the description of this animal as a monogastric, pseudo-ruminant herbivore.
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Systemic network for dietary inorganic phosphate adaptation among three organs. Pflugers Arch 2018; 471:123-136. [DOI: 10.1007/s00424-018-2242-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 11/26/2018] [Accepted: 11/27/2018] [Indexed: 12/22/2022]
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4
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Muscher-Banse AS, Breves G. Mechanisms and regulation of epithelial phosphate transport in ruminants: approaches in comparative physiology. Pflugers Arch 2018; 471:185-191. [PMID: 30009339 DOI: 10.1007/s00424-018-2181-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 07/06/2018] [Accepted: 07/09/2018] [Indexed: 01/25/2023]
Abstract
Ruminants have a unique utilization of phosphate (Pi) based on the so-called endogenous Pi recycling to guarantee adequate Pi supply for ruminal microbial growth and for buffering short-chain fatty acids. Large amounts of Pi enter the gastrointestinal tract by salivary secretion. The high saliva Pi concentrations are generated by active secretion of Pi from blood into primary saliva via basolateral sodium (Na+)-dependent Pi transporter type II. The following subsequent intestinal absorption of Pi is mainly carried out in the jejunum by the apical located secondary active Na+-dependent Pi transporters NaPi IIb (SLC34A2) and PiT1 (SLC20A1). A reduction in dietary Pi intake stimulates the intestinal Pi absorption by increasing the expression of NaPi IIb despite unchanged plasma 1,25-dihydroxyvitamin D3 concentrations, which modulate Pi homeostasis in monogastric species. Reabsorption of glomerular filtrated plasma Pi is mainly mediated by the Pi transporters NaPi IIa (SLC34A1) and NaPi IIc (SLC34A3) in proximal tubule apical cells. The expression of NaPi IIa and the corresponding renal Na+-dependent Pi capacity were modulated by high dietary phosphorus (P) intake in a parathyroid-dependent manner. In response to reduced dietary Pi intake, the expression of NaPi IIa was not adapted indicating that renal Pi reabsorption in ruminants runs at a high level allowing no further increase when P intake is diminished. In bones and in the mammary glands, Na+-dependent Pi transporters are able to contribute to maintaining Pi homeostasis. Overall, the regulation of Pi transporter activity and expression by hormonal modulators confirms substantial differences between ruminant and non-ruminant species.
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Affiliation(s)
- Alexandra S Muscher-Banse
- Department of Physiology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15/102, 30173, Hannover, Germany.
| | - Gerhard Breves
- Department of Physiology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15/102, 30173, Hannover, Germany
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5
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Storm AC, Kristensen NB, Røjen BA, Larsen M. Technical note: A method for quantification of saliva secretion and salivary flux of metabolites in dairy cows1. J Anim Sci 2013; 91:5769-74. [DOI: 10.2527/jas.2013-6865] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- A. C. Storm
- Department of Animal Science, Aarhus University, Foulum, DK-8830, Tjele, Denmark
| | - N. B. Kristensen
- Department of Animal Science, Aarhus University, Foulum, DK-8830, Tjele, Denmark
| | - B. A. Røjen
- Department of Animal Science, Aarhus University, Foulum, DK-8830, Tjele, Denmark
| | - M. Larsen
- Department of Animal Science, Aarhus University, Foulum, DK-8830, Tjele, Denmark
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Virkki LV, Biber J, Murer H, Forster IC. Phosphate transporters: a tale of two solute carrier families. Am J Physiol Renal Physiol 2007; 293:F643-54. [PMID: 17581921 DOI: 10.1152/ajprenal.00228.2007] [Citation(s) in RCA: 175] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Phosphate is an essential component of life and must be actively transported into cells against its electrochemical gradient. In vertebrates, two unrelated families of Na+ -dependent P(i) transporters carry out this task. Remarkably, the two families transport different P(i) species: whereas type II Na+/P(i) cotransporters (SCL34) prefer divalent HPO(4)(2-), type III Na(+)/P(i) cotransporters (SLC20) transport monovalent H2PO(4)(-). The SCL34 family comprises both electrogenic and electroneutral members that are expressed in various epithelia and other polarized cells. Through regulated activity in apical membranes of the gut and kidney, they maintain body P(i) homeostasis, and in salivary and mammary glands, liver, and testes they play a role in modulating the P(i) content of luminal fluids. The two SLC20 family members PiT-1 and PiT-2 are electrogenic and ubiquitously expressed and may serve a housekeeping role for cell P(i) homeostasis; however, also more specific roles are emerging for these transporters in, for example, bone mineralization. In this review, we focus on recent advances in the characterization of the transport kinetics, structure-function relationships, and physiological implications of having two distinct Na+/P(i) cotransporter families.
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Affiliation(s)
- Leila V Virkki
- Institute of Physiology and Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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7
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Cho G, Nakae Y, Ishikawa Y. [The mechanisms that underlie xerostomia and the translocation of aquaporin]. Nihon Yakurigaku Zasshi 2006; 127:267-72. [PMID: 16755078 DOI: 10.1254/fpj.127.267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
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8
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Homann V, Rosin-Steiner S, Stratmann T, Arnold WH, Gaengler P, Kinne RKH. Sodium-phosphate cotransporter in human salivary glands: Molecular evidence for the involvement of NPT2b in acinar phosphate secretion and ductal phosphate reabsorption. Arch Oral Biol 2005; 50:759-68. [PMID: 15970207 DOI: 10.1016/j.archoralbio.2005.01.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Accepted: 01/15/2005] [Indexed: 11/19/2022]
Abstract
OBJECTIVE In order to elucidate the cellular and molecular mechanisms of phosphate secretion by human salivary glands, the expression and intracellular distribution of sodium-phosphate cotransporters was investigated. DESIGN Total RNA was extracted from 33 parotid gland (PG) and 35 submandibular gland (SMG) samples and RT-PCR was performed using gene specific primers for all known sodium-phosphate cotransporters. An antibody was raised against an NPT2b epitope and the cellular and intracellular distribution was investigated by immunohistochemistry. RESULTS No mRNA for the type I cotransporter NPT1 was found. Out of the type II phosphate cotransporters only message for NPT2b but not for NPT2a or NPT2c could be detected in about the same number of samples (76% in PG versus 69% in SMG). Type III cotransporter mRNA was also found in both glands, PIT1 gave positive results for 93% of PG samples compared to 69% of SMG samples. For PIT2 also, a higher expression was found in PG than in SMG, although the difference was smaller (79% versus 51%). Immunostaining for NPT2b was found both in the acini and in the ducts, with a stronger reaction in the latter. In acinar cells, NPT2b was restricted to the basal-lateral plasma membrane, in duct cells, a broad band of reactivity was located in the apical part of the cell. CONCLUSIONS These findings suggest a secondary active secretion of phosphate into the primary saliva. Ductal cells appear to be able to reabsorb phosphate, thereby modifying the phosphate concentration in the final saliva.
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Affiliation(s)
- Veronika Homann
- Abteilung Epithelphysiologie, Max-Planck-Institut für molekulare Physiologie, 44139 Dortmund, Germany
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Mabjeesh SJ, Gal-Garber O, Milgram J, Feuermann Y, Cohen-Zinder M, Shamay A. Aminopeptidase N Gene Expression and Abundance in Caprine Mammary Gland is Influenced by Circulating Plasma Peptide. J Dairy Sci 2005; 88:2055-64. [PMID: 15905436 DOI: 10.3168/jds.s0022-0302(05)72882-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study examined the localization and the effect of circulating peptides on the expression of aminopeptidase N (EC 3.4.11.2) in caprine mammary gland. Four lactating goats in mid to late lactation were used in a crossover design and were subjected to 2 dietary treatments. Abomasal infusion of casein hydrolysate was used to increase the concentration of peptide-bound amino acid in the circulation. Samples of mammary gland tissue from each goat were taken by biopsy at the end of each treatment period to measure gene and protein expression of aminopeptidase N in the tissue. There were no measurable effects on feed intake and milk production for any of the treatments. Western blot analysis showed that aminopeptidase N is located on the basolateral side of parenchymal cells and not on the apical membranes. Abomasal infusion of casein hydrolysate caused a marked change in the profile of arterial blood free amino acids and peptide-bound amino acids smaller than 1500 Da. Abundance of aminopeptidase N mRNA and protein increased by 51 and 58%, respectively, in casein hydrolysate-infused goats compared with the control treatment. It was concluded that aminopeptidase N is one candidate actively involved in the mammary gland to support protein synthesis and milk production. In accordance with the nutritional conditions in the current experiment, it is suggested that aminopeptidase N expression is partly controlled by the metabolic requirements of the gland and postabsorptive forms of amino acids in the circulation.
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Affiliation(s)
- S J Mabjeesh
- Department of Animal Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot, Israel.
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Huber K, Roesler U, Muscher A, Hansen K, Widiyono I, Pfeffer E, Breves G. Ontogenesis of epithelial phosphate transport systems in goats. Am J Physiol Regul Integr Comp Physiol 2003; 284:R413-21. [PMID: 12388429 DOI: 10.1152/ajpregu.00357.2002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rapid development of precocial goats in the first weeks after birth requires an adequate adaptation of phosphate transport systems to maintain the P homeostasis at each developmental stage. Here we examined the age-related development of Na+-Pi transport systems in small intestines, kidneys, and parotid glands of goats. Kinetic parameters were determined by brush-border membrane vesicle uptake studies, and relative expression of NaPi type II mRNA and protein was recorded by molecular biological methods. High intestinal Pi transport capacity was already present on the first day of life. Within the first 3 wk of life there seemed to be a change in the type of Na+-dependent Pi transporter, and NaPi IIb was expressed increasingly up to the fifth month of life. Renal Na+-Pi transport capacity was also high at birth, and this was associated with high expression levels of NaPi IIa mRNA, indicating the important role of this transporter for renal Pi reabsorption. At weaning an increase in both intestinal and renal Na+-Pi transport balanced the increasing requirements for Pi to establish the endogenous Pi cycle. Salivary Pi concentration and parotid NaPi II mRNA rose markedly to guarantee an adequate Pi supply for rumen microbes. We concluded that the high demand for Pi in young goats was assured by high basal Na+-Pi transport capacity of small intestines and kidney expressed continuously during ontogenesis.
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Affiliation(s)
- Korinna Huber
- Department of Physiology, School of Veterinary Medicine Hannover, D-30173 Hannover, Germany.
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11
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Abstract
Membrane transport systems for P(i) transport are key elements in maintaining homeostasis of P(i) in organisms as diverse as bacteria and human. Two Na-P(i) cotransporter families with well-described functional properties in vertebrates, namely NaPi-II and NaPi-III, show conserved structural features with prokaryotic origin. A clear vertical relationship can be established among the mammalian protein family NaPi-III, a homologous system in C. elegans, the yeast system Pho89, and the bacterial P(i) transporter Pit. An alternative lineage connects the mammalian NaPi-II-related transporters with homologous proteins from Caenorhabditis elegans and Vibrio cholerae. The present review focuses on the molecular evolution of the NaPi-II protein family. Preliminary results indicate that the NaPi-II homologue cloned from V. cholerae is indeed a functional P(i) transporter when expressed in Xenopus oocytes. The closely related NaPi-II isoforms NaPi-IIa and NaPi-IIb are responsible for regulated epithelial Na-dependent P(i) transport in all vertebrates. Most species express two different NaPi-II proteins with the exception of the flounder and Xenopus laevis, which rely on only a single isoform. Using an RT-PCR-based approach with degenerate primers, we were able to identify NaPi-II-related mRNAs in a variety of vertebrates from different families. We hypothesize that the original NaPi-IIb-related gene was duplicated early in vertebrate development. The appearance of NaPi-IIa correlates with the development of the mammalian nephron.
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Affiliation(s)
- A Werner
- Department of Physiological Sciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom.
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12
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Nguyen HV, Beechey RB. Acetate and formate uptake into vesicles isolated from the basolateral region of the plasma membrane of ovine parotid acinar cells. Biochem Biophys Res Commun 1999; 259:606-10. [PMID: 10364465 DOI: 10.1006/bbrc.1999.0785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The transport of acetate and formate into plasma membrane vesicles derived from the basolateral face of the ovine parotid acinar cell has an absolute requirement for an anion to be present within the intravesicular space: bicarbonate, formate, acetate, propionate, and butyrate support the uptake of either acetate or formate. A pH gradient across the vesicle membrane, pHi 7.4, pH0 5.5, enhances the uptake of formate, but not acetate. There is no direct relationship between the rate of exchange and the degree of protonation of formate or acetate in the extravesicular medium. The process is saturable and can be inhibited by a range of functional group reagents. When mannitol is the main external osmoticum, the uptake of acetate and formate is still rapid; thus, no other ions are involved in the process apart from the external formate or acetate and the intravesicular anion. This activity could play a major role in the provision of energy in ruminant tissues.
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Affiliation(s)
- H V Nguyen
- Institute of Biological Sciences, University of Wales, Aberystwyth, SY23 3DD, Wales, United Kingdom
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13
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Eguchi T, Ishikawa Y, Ishida H. Mechanism underlying histamine-induced desensitization of amylase secretion in rat parotid glands. Br J Pharmacol 1998; 124:1523-33. [PMID: 9723967 PMCID: PMC1565538 DOI: 10.1038/sj.bjp.0701981] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Histamine acted on H2 receptors in rat parotid tissues and induced the amylase secretion. Immunoblot analysis by using anti-H2 receptor protein antiserum demonstrated that histamine induced the increase and decrease in the amounts of H2 receptor proteins in basolateral and intracellular membranes, respectively. 2. Short-term treatment with histamine resulted in decreases in amylase secretion, the density of H2 receptors and their affinity for the agonists during further incubation with histamine, but showed an unaltered secretory response to isoproterenol, indicating that the histamine-induced desensitization was confined to H2 receptors. 3. This treatment triggered a 20% decrease in the histamine-stimulated adenylate cyclase activity and a 40% decrease in the phosphorylation level of Gi2alpha protein in the tissues, resulting in an increase in pertussis toxin (IAP)-catalyzed ADP-ribosylation of the protein. An enhancement of cholera toxin-catalyzed ADP-ribosylation of Gs protein was observed only during the first incubation with histamine. 4. This treatment triggered a 30% decrease and a 60% increase in the histamine-stimulated activities of protein kinase A and protein phosphatase 2A in the tissues, respectively. 5. Pretreatment with okadaic acid completely blocked the histamine-induced decrease in amylase secretion and increase in IAP-catalyzed ADP-ribosylation of Gi protein. The levels of Gi2alpha and Gs alpha proteins in the tissues were not modified by histamine treatment and the level of Gi2alpha protein was not affected by pretreatment with okadaic acid, as assessed by immunoblot analyses with anti-Gi2alpha and anti-Gs alpha protein antiserum. 6. The regulation of Gi2alpha protein phosphorylation in parotid tissues plays an important role in the histamine-induced desensitization of amylase secretion.
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Affiliation(s)
- T Eguchi
- Department of Pharmacology, Tokushima University School of Dentistry, Tokushima City, Japan
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14
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Ishikawa Y, Eguchi T, Skowronski MT, Ishida H. Acetylcholine acts on M3 muscarinic receptors and induces the translocation of aquaporin5 water channel via cytosolic Ca2+ elevation in rat parotid glands. Biochem Biophys Res Commun 1998; 245:835-40. [PMID: 9588201 DOI: 10.1006/bbrc.1998.8395] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To evaluate the role of aquaporin5 (AQP5) in salivary secretion induced by cholinergic stimulation, the alteration of the distribution of AQP5 in rat parotid tissues induced by acetylcholine (ACh) was studied by immunobolt analysis. The treatment of the tissues with ACh within 1 min induced the translocation of AQP5 from intracellular membranes (ICM) to apical membranes (APM), but that for more than 5 min resulted in the converse translocation from APM to ICM. The ACh-induced increase in the amount of AQP5 in APM was inhibited by atropine, p-F-HHSiD and TMB-8, but not by methoctramine, staurosporine or H-7. The calcium ionophore A-23187 alone stimulated the translocation of AQP5 between APM and ICM. These results indicated that ACh acted on M3 muscarinic receptors and induced the translocation of AQP5 between ICM and APM, and that the cytosolic Ca2+ elevation by ACh may play a key role in this translocation in rat parotid glands.
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Affiliation(s)
- Y Ishikawa
- Department of Pharmacology, Tokushima University School of Dentistry, Japan.
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15
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Elger M, Werner A, Herter P, Kohl B, Kinne RK, Hentschel H. Na-P(i) cotransport sites in proximal tubule and collecting tubule of winter flounder (Pleuronectes americanus). THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:F374-83. [PMID: 9486233 DOI: 10.1152/ajprenal.1998.274.2.f374] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Localization of a recently described and cloned Na-Pi cotransport system from flounder was investigated by reverse transcription-polymerase chain reaction (RT-PCR) of microdissected tubules and by immunocytochemistry of kidney of winter flounder. Histological examination showed a small glomerulus, an extremely short proximal tubule PI with a selective affinity to Lens culinaris agglutinin from lentils, and an extensive second proximal tubule segment PII (> 90% of proximal tubules), consisting of cells with numerous apical clear vesicles and extensive amplification of basolateral cell membranes. PII merged with the collecting tubule/ collecting duct (CT/CD) system without a distal segment. By RT-PCR, PII cells revealed high levels of NaPi-II related RNA; low levels were also observed in CTs. Previously characterized antisera against different epitopes of flounder NaPi-II specifically labeled the basolateral regions of PII and the apical cell portion of CT/CD cells and of some PII cells. These results suggest that tubular secretion of P(i) occurs in PII of teleost fish with modulation of urinary P(i) content in the subsequent CT/CD system.
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Affiliation(s)
- M Elger
- Institut für Anatomie und Zellbiologie I, Universität Heidelberg, Germany
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16
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Watkins DT, Cooperstein SJ. Effects of calcium and calmodulin on the binding of rat parotid secretion granules to the plasma membrane. J Dent Res 1997; 76:744-53. [PMID: 9109823 DOI: 10.1177/00220345970760030601] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Since numerous studies suggest that Ca++ and calmodulin may modulate the fusion of secretion granules to the plasma membrane which takes place in exocytosis, we have examined the role of calcium and calmodulin in the binding of isolated parotid secretion granules to plasma membrane vesicles. 125I-labeled inside-out plasma membrane vesicles were incubated with secretion granules, the mixture was layered over 20% sucrose, the gradient was centrifuged, and the amount of 125I in the granule pellet was determined. Addition of Ca++ (20 nM to 10 microM) produced a concentration-dependent increase in the binding of 125I-labeled plasma membrane vesicles to the secretion granules, reaching a maximum value at 10 microM free Ca++; half-maximal binding occurred at 400 nM. Neither right-side-out parotid plasma membrane vesicles nor inside-out pancreatic islet plasma membrane vesicles bound to granules in the presence of 1 microM Ca++. Calmodulin produced a concentration-dependent increase in binding above that of Ca++ alone, and this effect was inhibited by the calmodulin antagonists, trifluoperazine and calmidazolium. Incubation of secretion granules with octadecylrhodamine B (R18)-loaded inside-out plasma membrane vesicles and 2 microM Ca++ caused de-quenching of fluorescence, indicating that the lipids in the granule membrane and the plasma membrane had intermixed. Added calmodulin increased the fluorescence two-fold above that with Ca++ alone. These results suggest that Ca++ and calmodulin may play a role in parotid gland exocytosis by modulating the interaction between the secretion granules and plasma membrane.
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Affiliation(s)
- D T Watkins
- Department of Anatomy, University of Connecticut Health Center, Farmington 06030, USA
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17
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Lambotte S, Veyhl M, Köhler M, Morrison-Shetlar AI, Kinne RK, Schmid M, Koepsell H. The human gene of a protein that modifies Na(+)-D-glucose co-transport. DNA Cell Biol 1996; 15:769-77. [PMID: 8836035 DOI: 10.1089/dna.1996.15.769] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Recently, a cDNA (pRS1) was cloned from pig kidney cortex that encodes a membrane-associated protein involved in Na(+)-coupled sugar transport. pRS1 alters sugar transport by SGLT1 from rabbit intestine or by SMIT from dog kidney which is homologous to SGLT1. In contrast, pRS1 does not influence transporters from other genetic families. We report the cloning of the intronless human gene hRS1 (6,743 bp), which encodes a 617-amino-acid protein with 74% amino acid identity to pRS1. By fluorescence in situ hybridization, hRS1 was localized to chromosome 1p36.1. The localization to one chromosome and Southern blot analysis of restricted genomic DNA suggest that there is only one RS1-homologous gene in humans. Functionality of hRS1 was demonstrated by co-expression experiments of hRS1 and SGLT1 from human intestine in oocytes from Xenopus laevis. They show that hRS1-protein inhibits Na(+)-D-glucose co-transport expressed by human SGLT1 by decreasing both the Vmax and the apparent Km value of the transporter. The analysis of the 5'-noncoding sequence of hRS1 revealed different enhancer consensus sequences that are absent in the SGLT1 gene, e.g., several consensus sequences for steroid-binding proteins.
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Affiliation(s)
- S Lambotte
- Max-Planck Institute für Biochemie, Martinsried, Germany
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18
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Shirazi-Beechey SP, Penny JI, Dyer J, Wood IS, Tarpey PS, Scott D, Buchan W. Epithelial phosphate transport in ruminants, mechanisms and regulation. Kidney Int 1996; 49:992-6. [PMID: 8691751 DOI: 10.1038/ki.1996.142] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- S P Shirazi-Beechey
- Institute of Biological Sciences, University of Wales, Dyfed, Scotland, United Kingdom
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Tarpey PS, Wood IS, Shirazi-Beechey SP, Beechey RB. Amino acid sequence and the cellular location of the Na(+)-dependent D-glucose symporters (SGLT1) in the ovine enterocyte and the parotid acinar cell. Biochem J 1995; 312 ( Pt 1):293-300. [PMID: 7492327 PMCID: PMC1136258 DOI: 10.1042/bj3120293] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The Na(+)-dependent D-glucose symporter has been shown to be located on the basolateral domain of the plasma membrane of ovine parotid acinar cells. This is in contrast to the apical location of this transporter in the ovine enterocyte. The amino acid sequences of these two proteins have been determined. They are identical. The results indicated that the signals responsible for the differential targeting of these two proteins to the apical and the basal domains of the plasma membrane are not contained within the primary amino acid sequence.
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Affiliation(s)
- P S Tarpey
- Institute of Biological Sciences, University of Wales, Aberystwyth, Dyfed, U.K
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Pinches SA, Gribble SM, Beechey RB, Ellis A, Shaw JM, Shirazi-Beechey SP. Preparation and characterization of basolateral membrane vesicles from pig and human colonocytes: the mechanism of glucose transport. Biochem J 1993; 294 ( Pt 2):529-34. [PMID: 8396917 PMCID: PMC1134487 DOI: 10.1042/bj2940529] [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: 01/30/2023]
Abstract
Membrane vesicles were isolated from the basolateral domains of pig and normal human colonocytes. The activity of the ouabain-sensitive K(+)-activated phosphatase, the basolateral membrane marker, was enriched 13-fold in these membrane vesicles over the original homogenate. The membranes displayed cross-reactions with antibodies to the (Na+/K+)ATPase and the RLA class I major histocompatibility antigen, both known indicators of the basolateral membrane. There was negligible contamination by other organelles and the luminal membrane, as revealed by marker-enzyme analysis and Western blotting, using an antibody to villin. The vesicles transported D-glucose in a cytochalasin B-inhibitable Na(+)-independent manner, with a Km of 28.1 +/- 0.8 mM and Vmax. of 3.1 +/- 0.4 nmol/s per mg of protein. The transport was inhibited by 2-deoxy-D-glucose and 3-O-methyl-D-glucose, but not by L-glucose or methyl-alpha-D-glucose. Probing the colonocyte basolateral membranes with an antibody against the C-terminus of the human liver GLUT 2 produced a cross-reaction at 52 kDa. These properties indicate the presence of a GLUT 2 isoform on the basolateral membranes of human and pig colonocytes.
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Affiliation(s)
- S A Pinches
- Department of Biochemistry, University of Wales, Aberystwyth, Dyfed, U.K
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