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)

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

A method was developed to measure the element content of freshly isolated papillary collecting duct (PCD) cells by electron probe microanalysis in a scanning electron microscope. After isolation, the cells were transferred onto a Thermanox support by centrifugation and the extracellular medium was removed by brief exposure to buffered ammonium acetate; cryofixation, freeze-drying, and coating with carbon followed. Under visual control in the scanning electron microscope the Na, Cl, K and P content of cell clusters (about 30 cells/cluster) was then measured by X-ray microanalysis. Cells incubated in control medium showed potassium:sodium ratios identical to those determined previously in cryosections of the same cells. In ouabain-treated cells sodium influx and potassium efflux was demonstrated. Potassium left the cells with a t1/2 of 21.7 min. The t1/2 of Na influx was 12.6 min for the first 15 min of incubation, whereafter further influx was markedly slower. Ouabain-induced sodium influx was inhibited 40% by amiloride. These results indicate that X-ray microanalysis can be applied to analyze the ion content of isolated cell clusters derived from the papillary collecting duct. Using ouabain and amiloride as inhibitors the suitability of the method to identify transport systems is demonstrated.
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PMID:Measurement of element content in isolated papillary collecting duct cells by electron probe microanalysis. 292 90

The effect of streptozotocin-induced diabetes mellitus on rat renal ouabain-sensitive ATPase in six distinct nephron segments was studied. Twenty-four hours after administration of streptozotocin, blood glucose increased threefold (P less than 0.001), and glucosuria was evident. Aldosterone levels increased almost twofold (P less than 0.001). Ouabain-sensitive ATPase increased in the proximal segments PC (proximal convoluted tubule) and PS (proximal straight tubule) by 43 and 62%, respectively, (P less than 0.001) and CD (cortical collecting duct) ouabain-sensitive ATPase increased 77% (P less than 0.001). Ouabain-sensitive ATPase in the cortical (CTAL) and medullary (MTAL) thick ascending limbs of Henle's loop and in the DC (distal convoluted tubule) remained unchanged after 24 h of streptozotocin administration. Eight days after streptozotocin administration, when glomerular filtration rate (GFR) was already markedly elevated, ouabain-sensitive ATPase remained increased in the PC, PS, and CD but was significantly less compared with the activity after 24 h (P less than 0.05), whereas in the CTAL and MTAL a marked increase in ouabain-sensitive ATPase occurred by 54% in the CTAL and 65% in the MTAL (P less than 0.001). Aldosterone levels remained elevated compared with control but less than after 24 h. Pretreatment with deoxycorticosterone acetate abolished the increase in ouabain-sensitive ATPase in the CD. These findings show that streptozotocin-induced diabetes mellitus in the rat is associated with a substantial increase in ouabain-sensitive ATPase activity along most of the nephron. This increase in enzyme activity may represent a mechanism of physiological adaptation of the nephron to maintain electrolyte homeostasis in diabetes in face of the increased GFR and osmotic diuresis.
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PMID:Enhanced renal tubular ouabain-sensitive ATPase in streptozotocin diabetes mellitus. 301 97

The collecting duct system is a major site of ammonia addition to the tubule fluid. To study the mechanisms involved, we measured total ammonia and total CO2 transport in isolated, perfused cortical collecting ducts (CCD) from deoxycorticosterone-(DOC) treated rabbits. Perfusate and bath solutions contained 25 meq/liter HCO3 and 4 mM total ammonia. Net fluid transport was not significantly different from zero. Net secretion of total CO2 occurred in all tubules (mean collected concentration, 44.2 mM). Despite bicarbonate secretion, there was net secretion of total ammonia (mean collected concentration, 6.4 mM). There was no detectable ammonia addition to the collected fluid when ammonia was excluded from the perfusate and bath, ruling out a major contribution from synthesis. Ouabain did not significantly affect net transport of total ammonia or total CO2. To test the hypothesis that an acid pH disequilibrium may lower the luminal pH enough to drive ammonia secretion by nonionic diffusion, we perfused CCD from DOC-treated rabbits with carbonic anhydrase (CA) (0.1 mg/ml). Without CA, there was net total ammonia secretion (-2.2 pmol X min-1 X mm-1) and net total CO2 secretion (-16.6 pmol X min-1 X mm-1). Luminal CA converted the net total ammonia secretion to net absorption (1.0 pmol X min-1 X mm-1) while the bicarbonate secretion persisted (-11.2 pmol X min X mm-1). We conclude that total ammonia secretion in these tubules occurs primarily by diffusion of NH3 and is dependent on a luminal acid pH disequilibrium.
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PMID:Mechanism of ammonia secretion by cortical collecting ducts of rabbits. 609 87

The distribution and activities of phosphatases and oxidative enzymes have been determined with the help of histochemical methods in the kidney of the Prussian Carp, a stenohaline freshwater-fish. In addition to fish maintained in freshwater aquaria, a group of the animals used has been adapted to seawater of moderate salinity. The following pattern of enzyme reaction intensities has been observed in the various kidney structures: Strong reactions of alkaline phosphatase in the nephron are confined to the glomerular capillary convolute and the brush border of proximal segments. Equally enzyme activities are observed in the connective tissue sheath of the collecting duct -- archinephric duct system. Acid phosphatase can be detected in all segments of the nephronic tubule, strong activities are found in the proximal segment (P I), in the epithelium of the archinephric duct, and, especially, in the interstitial tissue. ATPase reacts strongly positive in epithelial cells of the distal tubule and the collecting duct -- archinephric duct system. ATPase reactions are inhibited by Ouabain, and therefore can be regarded as reactions of Na--K-ATPase. Mitochondrially bound oxidative enzymes, connected with the citric acid cycle and the respiratory chain, show very strong reaction intensities in the distal tubule and the collecting duct- archinephric duct system, while the glomeruli generally exhibit negative reactions. Lactate -- and malate dehydrogenases are found to react weakly to negatively throughout the whole kidney. Maintenance in seawater does not deeply affect the enzyme pattern of the kidney of the Prussian carp, with exception of some oxidative enzymes, reacting weaker in the distal tubule and the collecting duct-archinephric duct system. In addition, the epithelial cells of the archinephric duct of seawater adapted fish show a marked apical localization of reaction products for these enzymes. Possible relations between enzyme histochemistry and fish kidney physiology are discussed, in connection with comparative aspects of the enzyme histochemistry of the vertebrate kidney. A short review of normal histology and function of the kidney of the Prussian carp is added.
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PMID:[Phosphatases and oxidative enzymes in the kidney of the Prussian carp (Carassius auratus gibelio Bloch) adapted to salt water]. 625 47

Because a ouabain-sensitive H-K-adenosinetriphosphatase (H-K-ATPase) has been identified recently in the amphibian bladder, we evaluated whether such an ATPase might exist also in the mammalian kidney, along with the ouabain-insensitive H-K-ATPase previously described in the collecting duct. For this purpose, we searched for an Na-independent, K-stimulated, ouabain- and Sch-28080-inhibitable ATPase activity in single segments of rat nephron. Ouabain-sensitive K-stimulated ATPase activity was detected in the absence of Na+ in rat proximal convoluted and straight tubules and in medullary and cortical thick ascending limbs of Henle's loop but not in collecting ducts. This K-ATPase differs from Na-K-ATPase by 1) its absence of requirement for Na, 2) its sensitivity to Sch-28080, 3) its higher sensitivity to ouabain, and 4) its absence in the collecting duct. It differs from the collecting duct H-K-ATPase by 1) its distribution along the nephron, 2) its sensitivity to ouabain, and 3) its lower sensitivity to Sch-28080. Furthermore, in rats fed a K-depleted diet for 2 wk, ouabain-sensitive K-ATPase activity was markedly reduced in both proximal tubules and thick ascending limbs, whereas collecting duct H-K-ATPase was upregulated.
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PMID:Ouabain-sensitive and -insensitive K-ATPases in rat nephron: effect of K depletion. 761 55

The interaction of K+ and NH+4 on the basolateral membrane of cultured rat inner medullary collecting duct cells (IMCD) was explored using 86Rb+ as a K+ congener. Ouabain addition decreased Rb+ uptake to 22.0 +/- 2.6% of control. Possible ouabain-sensitive NH+4 transport was therefore explored. Replacement of N-methyl-D-glucamine chloride with NH4Cl or KCl decreased both total and ouabain-sensitive Rb+ uptake. This inhibition of Rb+ uptake by NH+4 was not due to changes in intracellular pH or differences in cell viability. We conclude that NH+4 competes with K+ for binding on the Na(+)-K(+)-adenosinetriphosphatase (ATPase). An inhibitory constant (Ki) for NH+4 of 11.0 +/- 1.6 and a Michaelis constant (Km) for K+ of 1.9 +/- 0.7 mM were measured. To extend these observations, NH+4 was tested as a substrate for ouabain-sensitive ATPase activity in native permeabilized IMCD cells. With 20 mM K+, activity was 202 +/- 73 nmol ATP hydrolyzed.min-1.mg protein-1, and with 20 mM NH+4, activity was 259 +/- 81 nmol ATP hydrolyzed.min-1.mg protein-1. Thus NH+4 substitution for K+ on the Na(+)-K(+)-ATPase is a likely mechanism for NH+4 uptake by the IMCD.
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PMID:NH+4 transport mediated by Na(+)-K(+)-ATPase in rat inner medullary collecting duct. 794 62

The postnatal maturation of Na transport in the rabbit cortical collecting duct (CCD) was investigated. CCD segments from rabbits of three different age groups (3-9 days, 10-15 days, and 22-27 days) were perfused in vitro. Lumen-to-bath 22Na fluxes were 38.5 +/- 4.7, 17.0 +/- 2.9, and 30.2 +/- 4.0 pmol.mm-1.min-1 in the three groups, respectively. The high flux in the youngest group was explained by a high passive flux (28.3 +/- 4.2 pmol.mm-1.min-1) determined in the presence of ouabain; the passive 22Na flux in the two other groups (7.1 +/- 2.6 and 3.1 +/- 2.4 pmol.mm-1.min-1) was not significantly different from previously reported adult values. Ouabain-sensitive 22Na flux, reflecting active transport, was low in the two younger groups (10.3 +/- 2.5 and 9.9 +/- 1.9 pmol.mm-1.min-1), but exhibited a rapid increase to 27.1 +/- 2.6 pmol.mm-1.min-1 by 22-27 days of age. In vivo glucocorticoid pretreatment did not affect the Na transport in any age group. Mineralocorticoid pretreatment for 2 days had no effect in the two younger groups, but increased lumen-to-bath 22Na flux from 30.2 +/- 4.0 to 51.1 +/- 4.3 pmol.mm-1.min-1 in the 22- to 27-day-old group. The findings demonstrate that the maturation of rabbit CCD Na transport occurs in two stages, with the first consisting of a decrease in passive permeability during the first 2 wk of life, followed by an increase in active transport and simultaneous development of mineralocorticoid responsiveness.
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PMID:Ontogeny of cortical collecting duct sodium transport. 804 64

Urinary obstruction markedly reduces collecting duct Na+ reabsorption. To define the cellular mechanisms of this derangement in Na+ reabsorption in inner medullary collecting duct (IMCD) of obstructed kidneys, suspensions of intact IMCD cells and inner medulla plasma membranes (IMPM) were prepared from 24 h obstructed and untreated control kidneys. Oxygen consumption (QO2) studies revealed marked reductions in both amiloride-sensitive and ouabain-sensitive QO2 but not ouabain-insensitive QO2 in intact IMCD cells from obstructed, compared with control animals, indicating a reduction in oxygen-dependent transport activities of both the Na+ channel and the Na(+)-K(+)-adenosinetriphosphatase (ATPase). Amiloride-sensitive conductive 22Na+ uptake in intact IMCD cells from obstructed kidneys was significantly decreased by 45% at 10 s, 30 s, and 1-5 min (10 s: 2.42 +/- 0.63 vs. 4.49 +/- 0.64 nmol Na+ flux/mg protein, n = 7, P < 0.05; 1 min: 4.65 +/- 0.7 vs. 8.27 +/- 0.98 nmol Na+ flux/mg protein, n = 7, P < 0.05), indicating decreased activity of amiloride-sensitive Na+ channels in these cells. However, immunoblots of IMPM with antibodies to Na+ channel proteins did not show significant differences in content of Na+ channel proteins between membranes from obstructed and control groups. Ouabain-sensitive Na(+)-K(+)-ATPase activity in IMPM of obstructed kidneys was also reduced (61.1 +/- 18.1 vs. 152.6 +/- 25.8 nmol ATP degradation.min-1.mg protein-1, n = 6, P < 0.02), and immunoblots with monoclonal antibodies against the alpha 1- and beta-subunits of rabbit Na(+)-K(+)-ATPase showed a 51 +/- 7% reduction of both subunits in IMPM from obstructed kidneys (n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transport defects of rabbit inner medullary collecting duct cells in obstructive nephropathy. 838 52

Cisplatin (CP) nephrotoxicity in vivo is characterized by proximal tubule (PT) and collecting duct dysfunction. We reported previously that mitochondrial injury is an important early event in CP toxicity to PT cells and precedes inhibition of Na+,K(+)-ATPase activity and loss of cell K+. In the present study, we monitored oxygen consumption (QO2) and net K+ fluxes in intact inner medullary collecting duct (IMCD) and PT cells in vitro, using O2- and K(+)-sensitive electrodes, to determine if CP has similar effects on IMCD cells. Short-term exposure of IMCD cells to CP resulted in inhibition of spontaneous, ouabain-sensitive and ouabain-oversensitive QO2, but to a lesser degree than in PT. Ouabain-sensitive K+ transport and cell K+ content were also reduced in intact IMCD cells in this setting, confirming inhibition of Na+,K(+)-ATPase activity. In contrast, Na+,K(+)-ATPase activity measured in IMCD cell lysates was not altered. These results suggested that CP inhibited Na+,K(+)-ATPase activity in intact IMCD cells indirectly either by blocking Na+ entry or by inhibiting mitochondrial oxidative phosphorylation. Nystatin (Na+ ionophore) and carbonyl cyanide m-chlorophenylhydrazone (CCCP, uncoupler of oxidative phosphorylation) were used to distinguish between these possibilities. Nystatin-stimulated and CCCP-uncoupled QO2 were reduced in CP-treated IMCD cells by 34 +/- 10% and 25 +/- 5%, respectively, indicating mitochondrial injury. Again, the effects of CP on nystatin-stimulated and CCCP-uncoupled QO2 in IMCD cells were significantly less dramatic than in PT cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential actions of cisplatin on renal proximal tubule and inner medullary collecting duct cells. 838 66


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