Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study was undertaken to determine whether the change in cellular Na+ concentration ( [Na+]i) or cellular pH (pHi) is essential for the modulation by Na+/H+ antiporter of the cellular action of arginine vasopressin (AVP) in renal inner medullary collecting duct cells in culture. Extracellular Na+ depletion promptly decreased [Na+]i from 15.8 to 5.4 mM (P less than 0.01), which was closely related to the decrease in pHi (7.19 to 6.97; P less than 0.01). In the presence of 0.5 mM 3-isobutyl-1-methylxanthine, AVP increased cellular cAMP production in a dose-dependent manner. This was significantly blunted in the Na(+)-depleted cells (1 nM AVP; 481.9 vs. 341.0 fmol/micrograms protein; P less than 0.01). When cells were incubated with the Na(+)-depleted medium containing 25 mM NaHCO3, [Na+]i decreased promptly, but the pHi remained unchanged. Under this condition, the AVP-induced increase in cellular cAMP production was not altered (1 nM AVP; 390.9 vs. 334.8 fmol/micrograms protein). Also, after the Na(+)-depleted cells were incubated in 20 mM NH4Cl, which promptly normalized pHi despite the decreased [Na+]i, the response of cAMP production to AVP was restored. Amiloride (1 x 10(-5)-1 x 10(-3) M), which blocks the Na+/H+ exchange, decreased pHi and AVP- and forskolin-induced cAMP production in a dose-dependent manner. These results indicate that the decrease in [Na+]i promptly inhibits AVP-induced cAMP production mediated through the reduction in pHi in renal inner medullary collecting duct cells.
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PMID:pH dependence of inhibition of arginine vasopressin-induced adenosine 3',5'-monophosphate production by cellular sodium depletion in rat renal inner medullary collecting duct cells in culture. 130 26

To examine the mechanism by which mineralocorticoids regulate HCO3- absorption in the rabbit inner stripe of the outer medullary collecting duct, we microfluorometrically measured intracellular pH (pHi) in in vitro perfused tubules using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) assaying the apical and basolateral membrane H+/OH-/HCO3- transport processes in three groups of animals: those receiving chronic in vivo DOCA treatment (5 mg/kg per d x 2 wk); those with surgical adrenalectomy (ADX, [chronic x 2 wk]) on glucocorticoid replacement; and controls. Baseline pHi was not different in the three groups. Cellular volume (vol/mm) was increased 38% in DOCA tubules versus controls, but unchanged in ADX tubules versus controls. Buffer capacities (BT) were not different in the three groups. Apical membrane H+ pump activity, assayed as the Na(+)-independent pHi recovery from an acid load (NH3/NH4+ prepulse) and expressed as JH (dpHi/dt.vol/mm.BT) was increased 76% in DOCA tubules versus controls, and decreased 56% in ADX tubules versus controls. Basolateral membrane Cl-/HCO3- exchange activity assayed as the pHi response to basolateral Cl- addition was increased 73% in DOCA tubules versus controls, and decreased 44% in ADX tubules versus controls. When examined as a function of varying [Cl-], the Vmax of Cl-/HCO3- exchange activity was significantly increased in DOCA tubules (control, 72.7 +/- 15.7 pmol.mm-1.min-1 vs DOCA, 132.3 +/- 22.5 pmol.mm-1.min-1, P less than 0.02), while the K1/2 for Cl- was unchanged. Basolateral membrane Na+/H+ antiporter activity assayed as the Na(+)-dependent pHi recovery from an acid load was not changed in chronic DOCA tubules versus controls. In conclusion, the apical membrane H+ pump and basolateral membrane Cl-/HCO3- exchanger of the rabbit OMCDi are regulated in parallel without chronic alterations in pHi under the conditions of mineralocorticoid excess and deficiency. The parallel changes in these transporters accounts for the alterations in OMCDi HCO3- absorption seen under these conditions.
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PMID:Mineralocorticoid modulation of apical and basolateral membrane H+/OH-/HCO3- transport processes in the rabbit inner stripe of outer medullary collecting duct. 132 41

Cells from the inner stripe of the rabbit outer medullary collecting duct (OMCDi) were grown in primary culture, and their acid-base transport properties were characterized using intracellular pH (pHi) measurements with the fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Basal pHi in HCO(3-)-buffered solutions was 7.28 +/- 0.04 (n = 20). The presence of a Cl-/HCO(3-)-antiporter was demonstrated by reversible alkalinization on bath Cl- removal. The mean alkalinization seen on Cl- removal was 0.16 +/- 0.02 pH units (n = 20) and was inhibited 92% by 10(-4) M 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Studies were also performed to determine the presence of an Na+/H+ antiporter and an H(+)-adenosinetriphosphatase (H(+)-ATPase). After an NH4Cl acid load the cells exhibited both Na(+)-dependent and Na(+)-independent pHi recovery mechanisms. The Na(+)-dependent mechanism was inhibited by amiloride. The Na(+)-independent mechanism was completely inhibited by 10(-3) M N-ethylmaleimide or 2.5 x 10(-9) M bafilomycin A1, but was not significantly altered by removal of bathing solution K+. Thus, the Na(+)-dependent recovery mechanism exhibited characteristics of an Na+/H+ antiporter, whereas the Na(+)-independent recovery mechanism was consistent with the presence of an H(+)-ATPase.
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PMID:Characterization of acid-base transporters in cultured outer medullary collecting duct cells. 133 12

Primary cultures of rat renal inner medullary collecting duct cells were grown to confluence on glass coverslips and treated permeant supports, and the pH-sensitive fluorescent probe 2,7-biscarboxyethyl-5,6-carboxyfluorescein was employed to delineate the nature of the transport pathways that allowed for recovery from an imposed acid load in a HCO3-/CO2-buffered solution. The H+ efflux rate of acid-loaded cells was 13.44 +/- 0.94 mM/min. Addition of amiloride, 10(-4) M, to the recovery solution reduced the H+ efflux rate to 4.06 +/- 0.63 mM/min. The amiloride-resistant pHi recovery mechanism displayed an absolute requirement for Na+ but was Cl(-)-independent. Studies performed on permeable supports demonstrated that the latter pathway was located primarily on the basolateral-equivalent (BE) cell surface and was inhibited by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). In a Na(+)-replete solution containing DIDS (50 microM) and amiloride (10(-4) M), acid-loaded cells failed to return to basal pHi. To delineate further the amiloride-inhibitable component of pHi recovery, monolayers were studied in the nominal absence of HCO3-/CO2. In 70% of monolayers studied, Na(+)-dependent, amiloride-inhibitable H+ efflux was the sole mechanism whereby acid-loaded cells returned to basal pHi. A Na(+)-independent pathway was observed in 30% of monolayers examined and represented only a minor component of the pHi recovery process. In studies performed on permeable supports, the Na(+)-dependent amiloride-inhibitable pathway was found to be confined exclusively to the BE cell surface. In summary, confluent monolayers of rat renal inner medullary collecting duct cells in primary culture possess two major mechanisms that contribute toward recovery from an imposed acid load, namely, Na+/H+ antiport and Na+/HCO3- cotransport. Na(+)-independent pHi recovery mechanisms represent a minor component of the pHi recovery process in the cultured cell. Both the Na+/H+ antiporter and Na+/HCO3- cotransporter are located primarily on the BE cell surface.
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PMID:Polarized distribution of Na+/H+ antiport and Na+/HCO3- cotransport in primary cultures of renal inner medullary collecting duct cells. 184 27

Na+ entry into kidney epithelial cells occurs by a multiplicity of pathways. Established cell lines such as the A6 cells, derived from the collecting duct of the kidney of Xenopus laevis, MDCK cells, from the distal tubule of a dog kidney, and the LLC-PK1 cells, originating from the proximal tubule of a pig kidney, provide excellent model cell systems for the detailed characterization and isolation of the proteins which comprise these entry pathways. Major pathways of Na+ entry include the amiloride-sensitive Na+ channel, the amiloride-sensitive Na+/H+ antiporter, and the loop diuretic-sensitive NaCl/KCl symporter. While the former two systems have been shown to exhibit an apical location in epithelial cells so far examined, the last system may be localized to either the basolateral or apical surface, depending on the transport function of the cell. Nutrient/Na+ symporters such as the glucose, phosphate, and p-aminohippurate symporters may all be localized to the apical surfaces of proximal tubular cells, but other systems, including those specific for neutral amino acids, may predominate in the basolateral surface or be distributed between the two membranes. Studies concerned with the catalytic, structural, and regulatory properties of these transport systems serve not only to characterize the individual translocators in established cell lines, but also to suggest their physiological functions in intact kidney tissues.
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PMID:Sodium entry pathways in renal epithelial cell lines. 242 Nov 47

In the male reproductive tract, the epididymis plays an important role in mediating transepithelial bicarbonate transport and luminal acidification. In the proximal vas deferens, a significant component of luminal acidification is Na+-independent, and mediated by specific cells that possess apical vacuolar proton pumps. In contrast, luminal acidification in the cauda epididymidis is an Na+-dependent process. The specific apical Na+-dependent H+/base transport process(es) responsible for luminal acidification have not been identified. A potential clue as to the identity of these apical Na+-dependent H+/base transporter(s) is provided by similarities between the transport properties of the epididymis and the mammalian nephron. Specifically, the H+/base transport properties of caput epididymidis resemble the mammalian renal proximal tubule, whereas the distal epididymis and vas deferens have characteristics in common with renal collecting duct intercalated cells. Given the known expression of the Na+/H+ antiporter, NHE3, in the proximal tubule, and of the electroneutral sodium bicarbonate cotransporter, NBC3, in renal intercalated cells, we determined the localization of NHE3 and NBC3 in various regions of rat epididymis. NBC3 was highly expressed on the apical membrane of apical (narrow) cells in caput epididymidis, and light (clear) cells in corpus and cauda epididymidis. The number of cells expressing apical NBC3 was highest in cauda epididymidis. The localization of NBC3 in the epididymis was identical to the vacuolar H+-ATPase. The results indicate that colocalization of NBC3 and the vacuolar H+-ATPase is not restricted to kidney intercalated cells. Moreover, the close association of the two transporters appears to be a more generalized phenomenon in cells that express high levels of vacuolar H+-ATPase. Unlike NBC3, NHE3 was most highly expressed on the apical membrane of all epithelial cells in caput epididymidis, with less expression in the corpus, and no expression in the cauda. These results suggest that apical NBC3 and NHE3 potentially play an important role in mediating luminal H+/base transport in epididymis.
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PMID:Immunolocalization of NBC3 and NHE3 in the rat epididymis: colocalization of NBC3 and the vacuolar H+-ATPase. 1097 18