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 role of anion exchange in the regulation of intracellular pH (pHi) under base load and steady-state conditions was investigated in confluent monolayers of rat inner medullary collecting duct (IMCD) cells in primary culture using the pH-sensitive fluoroprobe 2,7-bis(carboxyethyl)-5(6')-carboxyfluorescein (BCECF). Recovery of pHi after imposition of a base load induced either by replacement of HCO3-/CO2 by N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) at the same extracellular pH (pHo) or deletion of Cl- from a HCO3-/CO2-buffered solution had an absolute requirement for Cl-, was Na+ independent, and was inhibited approximately 90% by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). When pHo was decreased by lowering HCO3- concentration in the constant presence of 5% CO2, the rate of decrement in pHi was significantly blunted in the absence of Cl-. Imposition of a positive or negative diffusion potential of equal but opposite magnitude did not modify the anion exchange rate, confirming the electroneutrality of the process. Under steady-state conditions, pHi of cells bathed in a HCO3-/CO2-buffered solution was 7.33 +/- 0.06, significantly lower than that of cells bathed in a nominally HCO3-/CO2-free buffer (7.50 +/- 0.04), indicating that under physiological conditions the pathway functions as a base extruder. In studies performed on cells grown on permeable supports, the anion exchange pathway was found to be confined exclusively to the basolateral-equivalent cell surface. In summary, confluent monolayers of rat IMCD cells in primary culture possess a Na(+)-independent, DIDS-inhibitable electroneutral Cl(-)-HCO3- exchange pathway that is confined to the basolateral cell surface. The transporter is an important determinant of steady-state pHi and is the predominant mechanism whereby the cell recovers from imposed elevations in pHi.
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PMID:Basolateral Na(+)-independent Cl(-)-HCO3- exchange in primary cultures of rat IMCD cells. 141 68

We examined the ability of HCO3- -CO2 to modify the potency of Cl- channel blockers in the renal cortical collecting duct (CCD) for the following two reasons. 1) From a practical point of view, there is, to our knowledge, no information regarding the effect of the HCO3- -CO2 buffer system on the potency of Cl- channel blockers. 2) We showed in the companion manuscript [Am. J. Physiol. 257 (Cell Physiol. 26): C94-C101, 1989] that HCO3- -CO2 stimulates transepithelial anion exchange in the CCD. Based on precedent in the literature, we postulated that HCO3- stimulates the basolateral membrane Cl- conductance. Here, we demonstrate that several Cl- channel blockers can reduce CCD Cl- self exchange when the solutions are buffered in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Concentrations of blockers producing 80% inhibition in HEPES, pH 7.4, produced only 20% inhibition in 25 mM HCO3- -CO2, pH 7.4. The ability of HCO3- -CO2 to reduce blocker potency had an IC50 of only 2 mM. We also examined interactions of HCO3- -CO2 and blockers with regard to the principal cell basolateral Cl- conductance. Blockers did not alter the Rb+ flux, a marker of K+ transport, but did reduce transepithelial conductance (GT), i.e., the blockers inhibited the principal cell basolateral Cl- conductance. As was the case with intercalated cell anion exchange, GT measurements indicated that HCO3- -CO2 impaired the ability of Cl- channel blockers to inhibit the principal cell Cl- conductance.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reduction in sensitivity to Cl- channel blockers by HCO3- -CO2 in rabbit cortical collecting duct. 247 50

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, KCl (nm/s); a small fraction is effected by Cl--HCO3- exchange and Cl- diffusion. We previously reported that changing from a CO2-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) bath to a 5% CO2-25 mM HCO3- bath stimulates Cl- self exchange. Here, we examine in further detail the individual components of the CO2-HCO3- system that stimulate KCl. Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated KCl by 70 +/- 19 nm/s, a delta KCl comparable to that induced by 1% CO2 (pH 7.12), 6% CO2 (pH 6.6), or 6% CO2-25 mM HCO3- (pH 7.4). The roles of intracellular pH (pHi) and HCO3- concentration were examined by clamping pHi using high K+ and nigericin. Increasing pHi from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased KCl by 71 +/- 17 nm/s. These results suggest that pHi might regulate anion exchange. However, during such a pHi-shift experiment, metabolically derived CO2 produces a concomitant change in intracellular HCO3- concentration [( HCO3-]i). To determine whether an increase in [HCO3-]i could stimulate Cl- self exchange, we replaced HEPES with 6% CO2-5 mM HCO3- isohydrically (pHi clamped at 6.9). With this increase in [HCO3-]i at constant pHi, KCl increased by 51 +/- 10 nm/s. These maneuvers had negligible effects on Cl- diffusion and Cl--HCO3- exchange. These experiments demonstrate that increases in cell [HCO3-] (or perhaps CO2) can stimulate transepithelial anion exchange.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct. 250 23

This study evaluated the role of H-K-adenosinetriphosphatase (H-K-ATPase) with chronic metabolic acidosis (CMA) in intercalated cells (ICs) of rabbit cortical collecting duct (CCD). CMA was induced by replacing drinking water with 75 mM NH4Cl in 5% sucrose for 10-14 days. CCDs isolated from CMA and control rabbits were split open and exposed to the intracellular pH (pHi) indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. In N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solutions, the resting pHi in ICs was similar for both groups. K-dependent pHi recovery (5 mM K, 140 mM N-methyl-D-glucamine) was monitored in response to a pulse of NH4Cl (10 mM). The K-dependent pHi recovery rate was threefold higher in CMAICs compared with controls and was abolished with the gastric H-K-ATPase inhibitor, Sch-28080 (10(-5) M). Polarity of the H-K-ATPase was studied in microperfused CMA and control CCDs. Luminal K-dependent pHi recovery was monitored in response to an acute pulse of NH4Cl in individual peanut lectin agglutinin (PNA)-binding ICs. The apical Sch-28080-inhibitable K-dependent pHi recovery rate was significantly greater in CMA ICs than control ICs. In summary, CMA enhances functional activity of an apical H-K-ATPase in PNA-binding ICs of rabbit CCD.
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PMID:Stimulation of apical H-K-ATPase in intercalated cells of cortical collecting duct with chronic metabolic acidosis. 878 Feb 58

Functional and immunocytochemical studies indicate that intercalated cells in the adult rabbit cortical collecting duct (CCD) possess an H-K-adenosinetriphosphatase (H-K-ATPase). Because growing subjects must retain K+ and excrete H+, we sought to determine whether H-K-ATPase is present in the CCD early in life and, if so, to assess its activity and polarity. H-K-ATPase activity was defined as the initial rate of Sch-28080-inhibitable K+-dependent cell pH (pHi) recovery observed, in the absence of Na+, in response to an in vitro acid load. Transporter activity was assayed in intercalated cells labeled with the pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein and apical cell surface marker rhodamine peanut lectin (PNA) in split-open CCDs isolated from neonatal and adult New Zealand White rabbits. In Na+-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered solutions (nominal absence of CO2/HCO3-), the rate of K+-dependent pH(i) recovery from a NH4Cl-induced acid load was similar in newborn (0.056 +/- 0.015 pH U/min, n = 9) and adult (0.060 +/- 0.019 pH U/min; n = 9, P = not significant) cells. This rate of K+-dependent pH(i) recovery was significantly reduced by 10-20 pM Sch-28080, an inhibitor of gastric H-K-ATPase, in both newborns (0.009 +/- 0.003 pH U/min, n = 7) and adults (0.013 +/- 0.007 pH U/min, n = 9) (P < 0.05 compared with rates in absence of inhibitor). To determine whether the location of the transporter is consistent with a role in K+ absorption and H+ secretion, pH(i) recovery of acutely acid-loaded intercalated cells in neonatal CCDs (n = 7) microperfused and bathed in the absence of Na+ and K+ was monitored after selective addition of K+ to either the luminal or basolateral membrane. Addition of 5 mM K+ led to a significantly greater rate of pH(i) recovery when it was added to the luminal rather than the peritubular solution (0.049 +/- 0.005 vs. 0.018 +/- 0.005 pH U/min, P < 0.05). We conclude that PNA-binding intercalated cells of the neonatal CCD possess H-K-ATPase activity, predominantly located in the apical membrane. This provides a mechanism for H secretion and K+ retention, processes required for growth.
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PMID:H-K-ATPase activity in PNA-binding intercalated cells of newborn rabbit cortical collecting duct. 912 92