UNIPROT:P41181 - FACTA Search

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

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

Sodium absorption in distal tubule segments was stimulated by increasing the distal delivery via infusion of hypertonic saline. In these animals, and in control rats, electrolyte concentrations in thick ascending limb cells, light and dark cells of the collecting duct in the outer and inner stripe of the outer medulla and in cells of the proximal straight tubule (outer stripe only) were studied. The measurements were performed by electron microprobe analysis of freeze-dried cryosections of the outer medulla. In addition, organic osmolytes (glycerophosphorylcholine, betaine and myo-inositol) were measured by high performance liquid chromatography in cortex and outer medulla. Augmented delivery of sodium chloride to the distal tubule was associated with increased sodium concentrations of thick ascending limb cells both in the outer and inner stripe and of medullary collecting duct light and dark cells in the outer stripe. While the sum of organic osmolyte concentrations was 28% higher in the outer medulla of the salt-loaded animals compared with controls, this value was unchanged in the renal cortex. These findings indicate that the primary event underlying stimulation of sodium absorption along the thick ascending limb during increased distal sodium delivery is enhanced entry of sodium across the apical cell membrane. This would be expected to lead to higher cell sodium concentrations and stimulation of basolateral active Na-K-exchange. The enhanced transport activity of outer medullary tubules may be associated with increased interstitial tonicities and intracellular retention of organic osmolytes.
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PMID:Effect of increased distal sodium delivery on organic osmolytes and cell electrolytes in the renal outer medulla. 148 81

After summarizing the progress which has been made with regard to the isolation and characterization of homogeneous cell populations from the kidney, a brief survey of current techniques available for the analysis of intracellular parameters is given. Special emphasis is thereby placed on the use of electron probe X-ray microanalysis to determine intracellular elements and on "in vivo" nuclear magnetic resonance to define metabolic pathways in isolated cells. These methods have been applied to study ion and substrate fluxes in isolated collecting duct cells and the response of these cells to changes in osmolality of the extracellular medium. This response involves initially fast water movements accompanied by changes in intracellular sodium and chloride but not potassium concentration. Longterm adaptation is achieved by the adjustment of the intracellular concentration of "organic osmolytes" such as sorbitol, myoinositol, glycerophosphorylcholine, and betaine through changes in the rate of efflux of these metabolites from the cell. In the last section the effect of experimentally induced diabetes mellitus on the osmoregulation in isolated collecting ducts is described.
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PMID:[Study of kidney function using isolated cells]. 217 22

Glycerophosphorylcholine (GPC) plays an important role in the osmoregulation of the renal inner medulla. Under hyperosmotic conditions, a striking increase in cellular GPC content is observed. In order to characterize the cellular events involved in GPC metabolism, we have studied the uptake of choline, a precursor of GPC, by freshly isolated rat inner medullary collecting duct (IMCD) cells at 300 mosmol/l. Choline uptake occurred by a single transport system with an apparent affinity (Km) of 80 microM and a maximal velocity (Vmax) of 120 pmol/microliter cell water/min. Hemicholinium-3, ethanolamine and N,N-dimethylethanolamine were potent inhibitors, but betaine had no effect. Choline uptake was not altered by the replacement of Na+ with N-methylglucamine+, suggesting a sodium-independent process. Addition of 50 mM KCl to the incubation medium to reduce the cell membrane potential inhibited choline uptake by 19 +/- 4% after 10 min. Increasing the extracellular osmolarity to 600 or 900 mosmol/l had no effect on the kinetic parameters of choline uptake. These results suggest that choline uptake into IMCD cells occurs by a sodium-independent transport system driven by the inside negative cell membrane potential. Furthermore, the increase in the GPC content under hyperosmotic conditions is not associated with increased activity of the transport systems of biosynthetic precursors.
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PMID:Choline transport in collecting duct cells isolated from the rat renal inner medulla. 227 17

Papillary collecting duct tubules were prepared in gram quantities from the papillae of dog and pig kidneys. Measurements of substrate and oxygen utilizations by these tubules under both aerobic and anaerobic conditions showed the potential for both glycolysis and oxidative phosphorylation. Oxygen is not necessary to maintain a normal adenosine 5'-triphosphate concentration, but oxidative phosphorylation contributes to more than 65% of the metabolism under aerobic conditions in the two species. Both phosphorus-31 and proton nuclear magnetic resonance spectra recorded from extracts of dog cortex, red medulla, and papilla showed a clear gradient from cortex to papilla for osmolytes, such as glycerophosphorylcholine, sorbitol, inositol, betaine, and sugar phosphates. Other molecules identified in the spectra included glucose, sorbitol, mannitol, lactate, glutamine, alanine, threonine, and adenosine 5'-triphosphate. Conventional biochemical measurements supported these findings. An increase in osmolality from 300 to 600 mosmol/kg H2O for 120 min did not increase the glycerophosphorylcholine and sorbitol concentrations of dog papillary collecting ducts in vitro, but a small effect of a 24-h dehydration was detected in vivo.
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PMID:Biochemical characterization and osmolytes in papillary collecting ducts from pig and dog kidneys. 324 Apr 11

Taurine is a beta-sulfonic amino acid that serves as a nutrient important for developing brain and retina and as an osmolyte in the medullary collecting duct. The activity of the taurine transport system is regulated by substrate supply and by the external osmolality; these two stimuli induce changes in taurine transport. Increased medium osmolality (500 mosmol) stimulates taurine uptake into MDCK cells but not LLC-PK1 cells. The enhanced taurine uptake that occurs in response to hyperosmolality is localized primarily to the basolateral surface of MDCK cells, whereas the adaptive response to medium taurine concentration is expressed on both the apical and the basolateral surfaces of both cell lines. The response of MDCK cells to medium osmolality requires protein synthesis and RNA transcription and is expressed in the presence of microtubular toxins. When cell monolayers were loaded with taurine by incubation in high-taurine medium before increasing medium osmolality, the expected increase in taurine uptake was blunted. Similarly, increased external beta-alanine (500 microM) also prevented the anticipated increase in taurine accumulation in response to hypertonicity; aminoisobutyric acid and betaine (500 microM) partially prevented the increase in taurine transport after hypertonicity, whereas L-alanine had no effect. The concentration of taurine or structurally similar analogs in the external medium might modify the response of taurine accumulation after exposure to hypertonic medium, in that taurine-replete cells behave differently than taurine-depleted cells. These studies indicate that there are at least tow distinct mechanisms involved in the regulation of taurine transport: external taurine concentration and medium osmolality, with taurine concentration seeming to be the predominant stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The relative roles of external taurine concentration and medium osmolality in the regulation of taurine transport in LLC-PK1 and MDCK cells. 753 66

The effect of 60 minutes of ischemia and subsequent reflow on cell electrolyte and water homeostasis in the rat renal outer medulla was studied by determining sodium, potassium, chloride and phosphorus concentrations and dry weights in individual tubule cells using electron microprobe analysis. HPLC was employed to measure glycerophosphorylcholine, betaine, inositol and sorbitol, as well as several free amino acids in cortical and outer medullary tissue. Ischemia caused cell sodium and chloride concentrations to rise and cell potassium and phosphorus concentrations and cell dry weights to fall. These changes were most pronounced in the proximal straight tubule (PST) cells, less in thick ascending limb (MAL) and outer medullary collecting duct (OMCD) dark cells and barely noticeable in OMCD light cells. Except for some PST cells these changes were almost completely reversed 60 minutes after reintroducing blood flow. After 24 hours of reperfusion the number of PST cells exhibiting deranged electrolyte homeostasis was greatly increased. The contents of glycerophosphorylcholine, betaine or inositol in the cortex and outer medulla were not affected immediately following ischemia. After 24 hours of reperfusion, the cortical contents of osmolytes were still normal, while outer medullary contents were reduced. Except for low glycine contents, the ischemia-induced changes in amino acid contents were reversed after 24 hours of reflow in the cortex, whereas in the outer medulla aspartate, glycine and taurine contents were diminished. These results indicate increasing manifestation of PST cell injury in the reflow period. The defective re-accumulation of organic osmolytes and free amino acids in the outer medulla during reflow may reflect reduced interstitial tonicities, or may be due to inappropriate cellular uptake, synthesis or/and release.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ischemia-induced changes in cell element composition and osmolyte contents of outer medulla. 756 12

In isolated inner medullary collecting duct (IMCD) cells the adaptation to changes in extracellular osmolarity involves alterations in intracellular content of organic osmolytes such as glycerophosphorylcholine (GPC), sorbitol and others. To elucidate the basis of such alterations, the metabolism of GPC in IMCD cells was investigated with the labeled GPC precursor [methyl-3H]choline. The lipids phosphatidylcholine (PC), lyso PC (LPC) and sphingomyelin (SM), as well as the non lipids phosphorylcholine (Pcholine), GPC and an unknown water-soluble compound could be identified as intermediates of choline metabolism. In pulse-chase experiments the radioactivity of PC expressed as specific activity was at a higher level than the other metabolites (> 10-fold after 1h). Extended chase incubations caused the specific activity of PC and LPC to decrease significantly. GPC was the only metabolite with a significant increase in specific activity under these conditions, suggesting that PC (via LPC) could be the precursor of GPC. In short-term pulse experiments the specific activity of PC and LPC was always significantly higher compared to the specific activity of GPC. Pulse chase incubations using phosphatidyl[methyl-3H]choline showed a significant decrease in specific activity of PC after 15 h accompanied by a significant increase in specific activity of LPC as well as GPC. Inhibition of the PC hydrolyzing enzyme phospholipase A2 revealed a significant increase in the specific activity of PC. For GPC, a significant decrease in the radioactive labeling could be detected. The total amount of PC decreased by 10% under these conditions whereas the amount of GPC decreased by 22% which was significantly higher because of GPC breakdown. GPC degradation was catalyzed by GPC: choline diesterase generating choline (and phosphoglycerol). Significant activity of GPC:phosphocholine diesterase could not be detected. Betaine synthesis from choline was also not present. The slowest, and probably rate-limiting reaction of GPC synthesis from choline may be the reaction of phosphocholine cytidylyltransferase generating CDP choline, since no radioactive CDP choline could be detected under any conditions. Thus, isolated IMCD cells possess the ability for the synthesis of GPC from choline via PC and LPC, as well as for the GPC degradation to choline (and phosphoglycerol). Significant experimental evidence for the occurrence of de-novo synthesis of GPC from choline or a precursor function of GPC for PC could not be detected. However, although the former possibility seems unlikely, a final proof is still lacking.
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PMID:Metabolism of the 'organic osmolyte' glycerophosphorylcholine in isolated rat inner medullary collecting duct cells. I. Pathways for synthesis and degradation. 850 26

Hypotonic shock (change of osmolality from 600 mosmol to 300 mosmol by lowering NaCl concentration) increases the release of organic osmolytes from isolated inner medullary collecting duct (IMCD) cells in the following sequence: taurine > betaine > sorbitol > myo-inositol > glycerophosphorylcholine (GPC). The role of G-proteins in regulating the hypotonicity-induced efflux was analysed by exposing cells to various concentrations of a G-protein inhibitor, pertussis toxin (PTX; 20-200 ng/ml), and a Gialpha-protein stimulator, mastoparan (10-50 microM). PTX diminished the hypotonic release of sorbitol and betaine by 43.2+/-9. 5% and 32.2+/-7.8% (n = 5), respectively. Efflux of GPC, myo-inositol and taurine was not significantly altered. Mastoparan (10 microM) increased osmolyte release under isotonic conditions such that release of betaine was increased 3.8-fold and that of sorbitol 2.1-fold, while GPC, myo-inositol and taurine effluxes were only slightly augmented. Under hypotonic conditions, mastoparan stimulated betaine release (1.86+/-0.2-fold, n = 5) but not that of sorbitol. As tested in connection with sorbitol and betaine release, the effect of mastoparan was abolished by PTX, but not the A23187-evoked sorbitol release. Like mastoparan, arachidonic acid increased the release of sorbitol and betaine under isotonic conditions, but under hypotonic conditions it only increased the release of betaine. As to the role of intracellular Ca2+, hypotonic shock evoked an intracellular Ca2+ peak which could be prevented by PTX. Mastoparan increased intracellular Ca2+ under isotonic conditions, whether the extracellular Ca2+ concentration was low or high. The results indicate that G-proteins are involved in regulating sorbitol and betaine efflux from IMCD cells. The G-proteins regulating sorbitol release are probably involved in generating the proper intracellular Ca2+ signal. Betaine efflux, which is independent of intracellular Ca2+, might be regulated by a G-protein-stimulated release of arachidonic acid. Thus, probably several G-proteins are involved in controlling organic osmolyte efflux from IMCD cells.
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PMID:Role of G-proteins in the regulation of organic osmolyte efflux from isolated rat renal inner medullary collecting duct cells. 901 28

A primary culture from rat renal IMCD cells was established to investigate the permeability characteristics of the luminal and contraluminal plasma membranes of the papillary collecting duct in vitro. Freshly isolated IMCD cells were grown on filters in a special "epithelial cell" medium. Confluency was proved with an epithelial volt/ohm meter. After 7 d of culture the transepithelial resistance reached more than 1000 omega x cm2. A polarization of the cells with regard to a basolateral localization of a lactate efflux system, and an L-alanine transport system was achieved. The hypotonicity-activated release systems for the organic osmolytes sorbitol and betaine were also located basolaterally, whereas taurine, glycerophosphorylcholine, and myo-inositol left the cells at both cell poles but with different capacity. Morphological observations revealed also that the monolayer was well differentiated. Thus, a model of a renal collecting duct epithelium was established which can be used to analyze polarized and differentiated transport processes across the epithelial cells and their plasma membranes.
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PMID:Properties of a polarized primary culture from rat renal inner medullary collecting duct (IMCD) cells. 955 40

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