Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acidification of the luminal fluid in the epididymis is believed to play an important role in sperm maturation. Previous studies have shown that specialized cells in the epithelium lining the epididymis contain high levels of carbonic anhydrase and that these cells have rod-shaped intramembraneous particles when examined by freeze fracture. Both of these features are characteristic of proton-transporting intercalated cells in the kidney collecting duct. We now show that apical cells in the head of the epididymis and clear cells in the body and tail of the epididymis express high levels of a vacuolar proton-pumping adenosinetriphosphatase on their apical plasma membranes and on intracellular vesicles. By analogy with kidney intercalated cells, these cell types may be specialized for acid secretion in the epididymis.
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PMID:A plasma membrane proton ATPase in specialized cells of rat epididymis. 141 77

Endothelin-1 (ET-1) may be an important factor in the regulation of inner medullary collecting duct (IMCD) physiology. This segment of the nephron synthesizes ET-1, expresses endothelin receptors, and responds to exogenous ET-1 by reducing Na(+)-K(+)-ATPase activity and water transport. Taken together, these findings suggest an autocrine role for ET-1 in the regulation of IMCD function; however, because of the polarized nature of the IMCD, it is not known if ET-1 secretion, receptors, and receptor activation occur on the same side of the cell. To examine this question, rat IMCD cells were grown to confluence on semipermeable membranes. These cells exhibited polar morphology with high transepithelial electrical resistances. Immunoreactive ET-1 was secreted primarily into the basolateral side. Furthermore, 125I-ET-1 bound predominantly to the basolateral surface. Finally, ET-1 (10(-8) M) stimulated prostaglandin E2 production only when added to the basolateral side. These data indicate, therefore, that ET-1 is capable of autocrine regulation of IMCD cells and that this effect occurs predominantly on the basolateral side.
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PMID:Endothelin-1 is an autocrine factor in rat inner medullary collecting ducts. 141 33

Electron microprobe analysis on freeze-dried cryosections was used to determine the effect of the loop diuretics torasemide and furosemide on intracellular electrolyte concentrations in individual cells of the outer and inner stripe of the outer medulla and on cell rubidium uptake, the latter a measure of basolateral Na-K-ATPase activity. In addition, the organic osmolytes glycerophosphorylcholine (GPC), betaine, inositol and sorbitol in cortex, outer medulla and inner medulla were measured using HPLC. Both loop diuretics significantly reduced sodium and chloride concentrations and rubidium uptake in thick ascending limb cells, but did not affect sodium concentration or rubidium uptake in the proximal straight tubule (PST) cells or in the light or dark cells of the outer medullary collecting duct (OMCD). Chloride concentrations in these cells (that is, PST cells, OMCD light and dark cells) were lowered by loop diuretics, albeit less than in thick ascending limb cells. Administration of both loop diuretics for only 20 minutes was sufficient to significantly depress tissue concentrations of GPC, betaine, and myo-inositol in the outer medulla and of GPC, betaine and sorbitol at the papillary tip. These results indicate that loop diuretics, presumably by blocking apical sodium entry, decrease thick ascending limb cellular sodium concentration and, as a consequence, reduce Na-K-ATPase activity as assessed by cell rubidium uptake. Although this has been shown previously in in vitro preparations, the present study confirms this for the first time in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of loop diuretics on organic osmolytes and cell electrolytes in the renal outer medulla. 145 80

Two populations of intercalated cells, type A and type B, are present in the rat cortical collecting duct (CCD). Type A cells are involved in proton secretion and contain an apical H(+)-adenosinetriphosphatase (ATPase) and a basolateral Cl(-)-HCO3- exchanger. Type B cells are believed to be involved in HCO3- secretion, which is mediated by a Cl(-)-HCO3- exchange process and is Cl- dependent. The aim of this study was to examine the morphological and immunocytochemical response of type B intercalated cells in the rat to increased delivery of Cl- to the CCD. This was accomplished by chronic infusion of a loop diuretic, bumetanide (30 mg.kg body wt-1.day-1), via an osmotic minipump, and simultaneous administration of 0.9% sodium chloride in the drinking water for 6 days. The kidneys were preserved by in vivo perfusion with a periodate-lysine-paraformaldehyde fixative and processed for horseradish peroxidase and protein A gold immunocytochemistry, using rabbit polyclonal antibodies against carbonic anhydrase II, proton ATPase, and band 3 protein. Chronic infusion of bumetanide in combination with a high salt intake was associated with significant changes in the intercalated cells. Type B cells were increased in size and exhibited numerous apical microvilli, increased basolateral membrane area, and marked cytoplasmic and basolateral labeling for H(+)-ATPase. In contrast, type A cells were small and had sparse apical microprojections. H(+)-ATPase immunolabeling was observed primarily over apical tubulovesicles, and there was decreased basolateral immunolabeling for band 3 protein and occasional labeling for band 3 in lysosome-like structures. These observations support the hypothesis that increased delivery of Cl- to the CCD is associated with stimulation of type B intercalated cells to secrete HCO3-. The observations in type A cells are consistent with the cells being in a resting or inactivated state.
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PMID:Immunocytochemical response of type A and type B intercalated cells to increased sodium chloride delivery. 153 33

We examined the effect of Cl- depletion metabolic alkalosis (CDA) on H(+)-ATPase and band 3 protein localization in intercalated cells (IC) of the rat cortical collecting duct (CCD) and the outer medullary collecting duct (OMCD). After 30 min of peritoneal dialysis against 0.15 M NaHCO3 to produce CDA, or Ringer bicarbonate to serve as controls (CON), both groups were infused intravenously with an 80 mM Cl- solution for 90 min. For CDA vs. CON, physiological parameters were as follows: plasma total CO2, 38.0 +/- 1.1 vs. 27.8 +/- 0.6 meq/l (P less than 0.001); urinary total CO2 excretion, 141 +/- 89 vs. 20 +/- 3 neq.min-1.100 g body wt-1; and urinary Cl- excretion, 20 +/- 10 vs. 486 +/- 144 neq.min-1.100 g body wt-1 (P less than 0.001). H(+)-ATPase was localized in thin sections using a rabbit polyclonal antibody against the 70-kDa subunit of bovine brain H(+)-ATPase. Band 3 protein was localized using a polyclonal antibody against the 43-kDa subunit of the cytoplasmic domain of human erythrocyte band 3 protein. In CON rats, H(+)-ATPase localized along the apical plasma membrane and over the apical cytoplasmic vesicles of type A ICs in the CCD and ICs of the OMCD. H(+)-ATPase was observed along the basolateral plasma membrane and over cytoplasmic vesicles throughout type B ICs. In CDA rats, H(+)-ATPase was only observed over apical cytoplasmic vesicles in type A ICs and in the majority of OMCD ICs. In type B ICs, H(+)-ATPase staining was intensified along the basal plasma membrane in CDA. Band 3 protein was consistently localized in the basolateral plasma membrane of all type A cells in the CCD and ICs of the OMCD in both CON and CDA. In summary, stimulation of HCO3- secretion in rats caused withdrawal of H(+)-ATPase from the apical plasma membrane and storage in apical cytoplasmic vesicles of ICs of the OMCD and type A ICs of the CCD. H(+)-ATPase appeared to be inserted into the basal plasma membrane of type B ICs. These findings suggest that, during correction of CDA, proton secretion by type A and OMCD ICs is suppressed and proton transport across the basolateral plasma membrane of type B ICs is stimulated.
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PMID:Response of intercalated cells to chloride depletion metabolic alkalosis. 153 35

Atrial natriuretic peptide (ANP)(31-67), a portion of the atrial peptide prohormone, circulates in humans, and its plasma level varies with atrial pressure. Like the more widely studied carboxy-terminal fragment ANP(99-126), ANP(31-67) stimulates natriuresis and diuresis. We examined the mechanism of this natriuresis by measuring the effects of ANP(31-67) on Na+ transport in cells of the rabbit inner medullary collecting duct (IMCD). ANP(31-67) (10(-8) M) caused a 26 +/- 4% inhibition of oxygen consumption (QO2); half-maximal inhibition occurred at 10(-11) M, suggesting a physiologic effect. This effect was not additive with either ouabain or amiloride, suggesting that it reflected inhibition of Na+ transport-dependent QO2. ANP(31-67) reduced the amphotericin-induced stimulation of QO2 consistent with inhibition by this peptide of the Na(+)-K(+)-ATPase. In addition, ANP(31-67) reduced ouabain-sensitive 86Rb+ uptake under Vmax conditions. Several lines of evidence indicated that PGE2, a known endogenous IMCD Na(+)-K(+)-ATPase inhibitor, mediates pump inhibition by ANP(31-67). Thus, ANP(31-67) inhibits Na+ transport by inhibiting the Na(+)-K(+)-ATPase of IMCD cells, an effect mediated by the generation of PGE2.
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PMID:Atrial natriuretic peptide(31-67) inhibits Na+ transport in rabbit inner medullary collecting duct cells. Role of prostaglandin E2. 153 29

Vacuolar H+ ATPases reside in the plasma membrane of several segments of the mammalian nephron. In the proximal tubule, H+ ATPase is located in both the brush-border microvilli and in subvillar invaginations, while in the collecting duct intercalated cells, it is primarily in plasmalemma-associated membranes. H+ ATPase isolated from bovine kidney brush border has a cluster of polypeptides of Mr greater than 31,000 found associated with the Mr = 31,000 subunit, whereas H+ ATPase isolated from microsomes dose not have the additional associated polypeptides (Wang, Z.-Q., and Gluck, S. (1990) J. Biol. Chem. 265, 21957-21965, 1990). In this study, we describe the production of several new monoclonal antibodies to the bovine vacuolar H+ ATPase Mr = 31,000 subunit. Two of the antibodies differed in reactivity to the cluster of Mr greater than 31,000 subunits found in purified bovine kidney brush-border H+ ATPase. Antibody E11 reacted with both the Mr = 31,000 and Mr greater than 31,000 subunits and stained renal brush border intensely. Antibody H8 did not react with the Mr greater than 31,000 polypeptides and did not stain brush border. The heterogeneity of the Mr greater than 31,000 subunits did not appear attributable to glycosylation or phosphorylation. These findings provide further evidence for heterogeneity of the Mr = 31,000 subunit in different renal membrane compartments and suggest a role for the Mr greater than 31,000 polypeptides specific to the brush-border microvilli.
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PMID:Immunologic evidence that vacuolar H+ ATPases with heterogeneous forms of Mr = 31,000 subunit have different membrane distributions in mammalian kidney. 153 41

Cells from connecting tubule and cortical collecting duct of rabbit kidney were isolated by immunodissection with mAb R2G9 and cultured on permeable filters. Confluent monolayers developed an amiloride-sensitive transepithelial potential difference of -50 +/- 1 mV (lumen negative) and a transepithelial resistance of 507 +/- 18 omega cm2. Transepithelial Ca2+ transport increased dose-dependently with apical [Ca2+] and, in solutions containing 1 mM Ca2+, the active transcellular Ca2+ transport rate was 92 +/- 2 nmol h-1 cm-2. Transcellular Ca2+ transport was dependent on basolateral Na+ (Nab+). Isoosmotic substitution of Nab+ for N-methylglucamine resulted in a concentration-dependent decrease in Ca2+ absorption, with maximal inhibition of 67 +/- 5%. A Hill plot of the Na(+)-dependence yielded a coefficient of 1.9 +/- 0.4, indicating more than one Na+ site on a Na(+)-dependent Ca2+ transport system. In addition, the absence of Cab2+ resulted in a significant increase in Ca2+ transport both in the presence and absence of Nab+. Added basolaterally, ouabain (0.1 mM) inhibited Ca2+ transport to the same extent as did Na(+)-free solutions, while bepridil (0.1 mM), an inhibitor of Na+/Ca2+ exchange, reduced Ca2+ transport by 32 +/- 6%. Methoxyverapamil, felodipine, flunarizine and diltiazem (10 microM) were without effect. Depolarisation of the basolateral membrane, by raising [K+]b to 60 mM, significantly decreased transcellular Ca2+ transport, which is indicative of electrogenic Na+/Ca2+ exchange. In conclusion, active Ca2+ transport in the collecting system of rabbit kidney is largely driven by basolateral Na+/Ca2+ exchange. However, a residual Ca2+ absorption of about 30% was always observed, suggesting that other Ca2+ transport mechanisms, presumably a Ca(2+)-ATPase, participate as well.
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PMID:Role of Na+/Ca2+ exchange in transcellular Ca2+ transport across primary cultures of rabbit kidney collecting system. 161 31

We investigated mechanisms of regulatory volume increase in fused Madin-Darby canine kidney (MDCK) cells, a cell line originally derived from renal collecting duct. The intracellular ion concentrations as well as the concentration of the volume marker tetramethylammonium+ were measured by means of ion-selective microelectrodes. Application of hypertonic Ringer bicarbonate solution (+150 mmol/l mannitol) resulted in cell shrinkage to 84 +/- 2% of the initial cell volume (shrinkage expected for an ideal osmometer = 66%), indicating a significant regulatory volume increase. During the first 90 s of the hypertonic stress, a transient increase in intracellular Na+ and HCO3- concentrations was observed. It was followed by a sustained increase in intracellular K+ and Cl- concentrations. Ouabain (0.1 mmol/l) as well as amiloride (1 mmol/l) reduced K+ accumulation significantly, whereas the H+/K(+)-ATPase inhibitor SCH 28080 had no effect. Hypertonic stress hyperpolarized the cell membrane potential by 19 +/- 2 mV, owing to the decrease of the ratio of Cl- conductance to K+ conductance of the cell membrane. We conclude: (a) acute hypertonic stress activates Na+/H+ exchange in MDCK cells; (b) transient alteration of intracellular Na+ and pH stimulates Na+/K(+)-ATPase and Cl-/HCO3- exchange, exchange, both leading to the sustained intracellular accumulation of KCl; (c) a high intracellular KCl concentration is maintained by the partial reversion of the Cl-/K+ conductance ratio of the plasma membrane.
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PMID:Hypertonicity in fused Madin-Darby canine kidney cells: transient rise in NaHCO3 followed by sustained KCl accumulation. 165 30

The inner medullary collecting duct (IMCD) is the most distal portion of the nephron and plays an important role in urinary net acid excretion. The terminal or distal two thirds of the IMCD is lined by a single cell type, now termed the IMCD cell, which not only secretes protons, but transports sodium and potassium and responds to many hormones. The IMCD may account for greater than 50% of the excreted acid under control conditions and, during acidosis, absolute acid secretion may increase fivefold. Conversely, during alkalemia, acid secretion by this segment is abolished. Thus, the IMCD responds appropriately to perturbations in systemic acid-base balance. Furthermore, models of renal tubular acidosis have been demonstrated along this nephron segment. Three transporters that are important in acid-base control, the Na+/H+ and the Cl-/HCO3- exchanger and an active proton pump, presumably an H(+)-adenosine phosphatase (ATPase), have been demonstrated in IMCD cells. The former two are situated in the basolateral membrane, while the latter is situated in the apical membrane. Only the proton pump is responsible for actual acid addition to the urine. The intracellular mechanisms that modulate the proton pump are just beginning to be defined. It is likely that acid secretory activity involves exocytic insertion of additional pumps, and is dependent on cell pH changes, which are the primary signal, and on changes in intracellular calcium concentration and calmodulin activity, which are the second messengers.
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PMID:Regulation of acidification in the rat inner medullary collecting duct. 165 87


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