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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Whole cell patch-clamp techniques were used to characterize the electrophysiological properties of cells from the inner stripe portion of the rabbit outer medullary collecting duct (OMCDi) grown in primary culture. With pipette and bathing solutions mimicking intracellular and extracellular fluid, the resting membrane voltage was -30 to -40 mV. The whole cell conductance exhibited slight outward rectification, and at the resting membrane voltage the cell conductance averaged 2.58 +/- 0.49 nS (n = 17). The major conductive ion species was Cl-. The Cl- conductance was also found to have a significant permeability to HCO3- and was inhibited by the Cl(-)-channel blockers diphenylamine carboxylic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. A small K+ conductance was also present, but no Na+ conductance was detected. Current generated by the H(+)-adenosinetriphosphatase (H(+)-ATPase) was quantitated. This current was dependent on the presence of ATP in the pipette. Dicyclohexylcarbodiimide, N-ethylmaleimide, and bafilomycin A1, inhibitors of the vacuolar H(+)-ATPase, also reduced this outward current in an ATP-dependent manner. The inhibitor-sensitive component of the outward current, a measure of the current generated by the H(+)-ATPase, was in the range of 35-100 pA/cell.
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PMID:Electrophysiological properties of cultured outer medullary collecting duct cells. 133 7

To clarify mechanisms of intracellular pH (pHi) regulation in outer stripe of outer medullary collecting duct (OMCDOS), isolated perfused OMCDOS of the rabbit were loaded with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), and single cell pHi was monitored by an image processing system. Initial pHi recovery rates (dpHi/dt, pH unit/s x 10(3)) after intracellular acid load made by NH4Cl prepulse were determined. In the absence of exogenous CO2-HCO3-, dpHi/dt was 12.3 +/- 0.9 (means +/- SE) in principal cells (PC), and 11.5 +/- 1.0 in intercalated cells (IC). In PC, total ambient Na+ removal halted pHi recovery (dpHi/dt = 0.6 +/- 0.5), and pHi recovered when Na+ was added to the basolateral (dpHi/dt = 14.7 +/- 0.8) but not to the luminal (dpHi/dt = 0.9 +/- 0.5) solutions. This bath Na+ effect was amiloride inhibitable. In IC, pHi recovered (dpHi/dt = 6.4 +/- 0.3) in the absence of ambient Na+. This pHi recovery was significantly reduced by luminal 0.5 mM N-ethylmaleimide (NEM) or 0.5 mM N,N'-dicyclohexylcarbodiimide (DCCD). Basolateral NEM or DCCD had no significant effect. Basolateral addition of Na+ significantly accelerated the pHi recovery. These data suggest the presence of basolateral Na(+)-H+ exchange in both PC and IC, and luminal NEM- and DCCD-sensitive H+ pump in IC of rabbit OMCDOS.
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PMID:Cell pH regulation in rabbit outer medullary collecting duct cells: mechanisms of HCO3(-)-independent processes. 226 Jun 83

The regulation of proton transport and cytosolic pH was studied in rat papillary collecting duct (PCD) cells in culture using a pH-sensitive fluorescence probe, 2,7-bis-carboxyethyl-5,6-carboxyfluorescein (BCECF). Data were obtained from confluent monolayers grown on glass coverslips and dipped in a HCO3- -free medium, pH 7.40. The resting intracellular pH (pHi) was 7.16 +/- 0.03 (n = 20). When PCD cells had been acidified by pretreatment with NH4Cl, pHi immediately recovered toward the resting value. Two mechanisms participated in this recovery: a Na+-dependent mechanism which could be inhibited by amiloride (indicative of Na+-H+ exchanger) and a Na+-independent process (a proton ATPase). The pHi recovery from acid loading was inhibited by amiloride to about 55% of the control recovery (half-maximal effect at 100 microM). The rate of pHi recovery after the readdition of Na+ to a sodium-free medium exhibited saturation kinetics (half maximal rate at 28 mM). Dicyclohexylcarbodiimide (DCCD), an inhibitor of a plasma membrane proton ATPase, and the depletion of cellular ATP induced by 2 mM potassium cyanide (KCN) also partially inhibited the rate of pHi recovery after cell acidification with a NH4Cl load. When PCD cells were treated with 1 mM DCCD, amiloride almost completely inhibited pHi recovery. Amiloride and the removal of external Na+ had induced a gradual fall in pHi to a new resting value and rapidly recovered when Na+ was added. We conclude that PCD cells grown in culture have at least two proton transport mechanisms: a Na+-H+ exchanger and a plasma membrane proton ATPase. The kinetics of these processes can be reliably assessed by the pH-sensitive fluorescent probe, BCECF. Both the Na+-H+ exchanger and the plasma membrane proton ATPase may contribute to urinary acidification.
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PMID:Dual regulatory mechanisms of proton transport in rat papillary collecting duct cells in culture. 255 3

To determine whether kidney membrane fractions contain an extramitochondrial anion-stimulated ATPase, we compared the pharmacological and kinetic properties of HCO3-ATPase activities in mitochondrial and microsomal fractions prepared from rabbit kidney cortex and outer medulla. The results indicated that this activity differed markedly in each type of fraction. Microsomal HCO3-ATPase was less sensitive than mitochondrial ATPase to azide, oligomycin, DCCD and thiocyanate, but was more sensitive to filipin and displayed different dependency towards ATP, magnesium and pH. Microsomal ATPase activity was stimulated by sulfite much more strongly than by bicarbonate, whereas mitochondrial activity was stimulated by both these anions to a similar extent. These results demonstrate the presence of an extramitochondrial HCO3-ATPase in kidney membrane fractions. HCO3-ATPase was also measured in single microdissected segments of the rabbit nephron using a radiochemical microassay previously developed for tubular Na, K-ATPase activity. An enzyme with the pharmacological and kinetic properties of the microsomal enzyme was detected in both proximal tubule, distal convoluted tubule and collecting duct, but the thick ascending limb was devoid of any detectable activity. Long-term DOCA administration markedly increased HCO3-ATPase activity in the distal convoluted and collecting tubule. The insensitivity of microsomal HCO3-ATPase to vanadate indicates that it belongs to the F0-F1 class of ATPases, and might therefore be involved in proton transport. This hypothesis is also supported by the localization of tubular HCO3-ATPase activity at the sites of urinary acidification.
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PMID:Presence of an extramitochondrial anion-stimulated ATPase in the rabbit kidney: localization along the nephron and effect of corticosteroids. 293 49

pH recovery in response to addition of and removal from NH4Cl was examined using 2',7'-bis(2-carboxy-ethyl)-5(6)-carboxyfluorescein fluorescence in primary cultures of inner medullary collecting duct (IMCD) cells from rat kidneys. In 0 K+, pH recovery rate was 0.012 +/- 0.010 U/min; in 5 mM K+, the recovery rate was greater at 0.065 +/- 0.013 U/min (P = 0.026). The H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) inhibitors omeprazole and Sch-28080 and the P-type ATPase inhibitor vanadate significantly inhibited pH recovery at 100, 10, and 5 microM, respectively. The vacuolar H(+)-ATPase inhibitor bafilomycin failed to inhibit pH recovery, but N-ethylmaleimide (NEM) did. A range of Sch-28080 concentrations inhibited ouabain-resistant ATPase activity of microsomes from these cells in a reverse sigmoidal manner, with little inhibition < 1 microM, virtually 100% inhibition > 100 microM, and a 50% inhibitory concentration of approximately 20 microM. Bafilomycin only produced significant inhibition of activity at concentrations well in excess of those that are effective against the vacuolar H(+)-ATPase. The ouabain-resistant ATPase activity in cultured IMCD was also sensitive to vanadate (90% inhibition with 5 microM) but relatively resistant to N,N'-dicyclohexylcarbodiimide and NEM. These results indicate that pH regulation in primary cultures of IMCD cells, presumably reflecting H+ transport, is predominantly due to an H(+)-K(+)-ATPase.
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PMID:H(+)-K(+)-ATPase of rat inner medullary collecting duct in primary culture. 823 50

It is now apparent that multiple genetic alterations, including oncogene activation and tumor suppressor gene inactivation, are necessary steps in carcinogenesis. We have studied this concept in renal cancers by looking at specific tumor suppressor genes implicated in several allelotyping studies. Primary, predominantly low stage renal tumors of varying grades and histologic subtypes were investigated for allelic loss of 3p, 17p and the p53 gene, the DCC gene and the Rb gene and its product. 3p loss occurred in 47% of tumors studied and was much more common in clear cell cancers (85%). 17p and p53 gene loss were relatively uncommon events with only 6 of 42 tumors demonstrating loss. None of the tumors with typical histologies had allelic loss of the DCC gene, though loss did occur in leiomyosarcoma and a collecting duct tumor. Allelic loss of the Rb gene occurred in one clear cell tumor, the leiomyosarcoma, and, interestingly, in both collecting duct tumors in this series. Allelic loss of the Rb gene was correlated with little or no RB protein expression as judged by immunohistochemistry. At all loci studied, allelic loss did not appear to correlate with tumor grade or stage. These results suggest that inactivation of the p53, Rb, and DCC genes by allelic loss are uncommon events in the early stages of renal carcinogenesis.
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PMID:Tumor suppressor gene allelic loss in human renal cancers. 837 15

The response of H+-ATPase to lethal acid stress is unknown. A mutant strain (called NHE2d) was derived from cultured inner medullary collecting duct cells (mIMCD-3 cells) following three cycles of lethal acid stress. Cells were grown to confluence on coverslips, loaded with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, and monitored for intracellular pH (pHi) recovery from an acid load. The rate of Na+-independent pHi recovery from an acid load in mutant cells was approximately fourfold higher than in parent cells (P < 0.001). The Na+-independent H+ extrusion was ATP dependent and K+ independent and was completely inhibited in the presence of diethylstilbestrol, N,N'-dicyclohexylcarbodiimide, or N-ethylmaleimide. These results indicate that the Na+-independent H+ extrusion in cultured medullary cells is mediated via H+-ATPase and is upregulated in lethal acidosis. Northern hybridization experiments demonstrated that mRNA levels for the 16- and 31-kDa subunits of H+-ATPase remained unchanged in mutant cells compared with parent cells. We propose that lethal acid stress results in increased H+-ATPase activity in inner medullary collecting duct cells. Upregulation of H+-ATPase could play a protective role against cell death in severe intracellular acidosis.
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PMID:Functional upregulation of H+-ATPase by lethal acid stress in cultured inner medullary collecting duct cells. 935 63