Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

By in vitro experiments on rabbit bladder, we reassessed the traditional view that mammalian urinary bladder lacks ion transport mechanisms. Since the ratio of actual-to-nominal membrane area in folded epithelia is variable and hard to estimate, we normalized membrane properties to apical membrane capacitance rather than to nominal area (probably 1 muF approximately 1 cm2 actual area). A new mounting technique that virtually eliminates edge damage yielded resistances up to 78,000 omega muF for rabbit bladder, and resistances for amphibian skin and bladder much higher than those usually reported. This technique made it possible to observe a transport-related conductance pathway, and a close correlation between transepithelial conductance (G) and short-circuit current (Isc) in these tight epithelia. G and Isc were increased by mucosal (Na+) [Isc approximately 0 when (Na+) approximately 0], aldosterone, serosal (HCO-3) and high mucosal (H+); were decreased by amiloride, mucosal (Ca++), ouabain, metabolic inhibitors and serosal (H+); and were unaffected by (Cl-) and little affected by antidiuretic hormone (ADH). Physiological variation in the rabbits' dietary Na+ intake caused variations in bladder G and Isc similar to those caused by the expected in vivo changes in aldosterone levels. The relation between G and Isc was the same whether defined by diet changes, natural variation among individual rabbits, or most of the above agents. A method was developed for separately resolving conductances of junctions, basolateral cell membrane, and apical cell membrane from this G--Isc relation. Net Na+ flux equalled Isc. Net Cl- flux was zero on short circuit and equalled only 25% of net Na+ flux in open circuit. Bladder membrane fragments contained a Na+-K+-activated, ouabain-inhibited ATPase. The physiological significance of Na+ absorption against steep gradients in rabbit bladder may be to maintain kidney-generated ion gradients during bladder storage of urine, especially when the animal is Na+-depleted.
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PMID:Na+ transport by rabbit urinary bladder, a tight epithelium. 0 12

The NA-K-ATPase of toad skin was characteristically sensitive to Na, K, and ATP. It was not affected by amiloride, vasopressin, cAMP, and thyroxine, but stimulated by insulin. Ouabain, a potent inhibitor at 37 degrees C, did not inhibit the enzyme activity significantly at 23 degrees C. The optimal pH for the enzyme activity increased as temperature decreased. However, the optimal OH-/H+ ratio of the medium remained constant at 16 regardless of temperature. The Km for ATP remained unchanged between 37 and 8 degrees C if the OH-/H+ ratio was held constant at 16, but increased as temperature decreased if the pH of the medium was held constant at 7.4. The enzyme activity showed no appreciable variation between 37 and 20 degrees C with a constant OH-/H+ ratio of 16, whereas it decreased logarithmically at a constant pH of 7.4 over the same temperature range. These results indicate the presence of a typical Na-K-ATPase system in toad skin and that the enzyme is in the most active catalytic state at a fixed level of OH-/H+ ratio in the medium regardless of incubation temperature.
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PMID:Properties of toad skin Na-K-ATPase with special reference to effect of temperature. 1 98

A membrane fraction enriched in parathyroid hormone (PTH)-sensitive adenylate cyclase and sodium and potassium ion-activated (Na+, K+)-ATPase was prepared from bovine kidney. Tritiated PTH binding to this membrane fraction was dependent on both hormone and membrane protein concentration. Both total and specific binding of the hormone decreased significantly after 5 to 10 min of incubation at 22 degrees. PTH binding was highly specific, being sensitive to inhibition only with active forms of unlabeled hormone (native and 1-34 PTH). Specific binding showed a pH optimum of 7.3 to 7.5. Inhibition of binding of tritiated hormone by unlabeled PTH was also highly effective at pH 6.0, but this apparently specific binding was also inhibited by adrenocorticotropic hormone, insulin, glucagon, and vasopressin. Dissociation of bound hormone was demonstrated, and an apparent dissociation constant of 4.6 X 10(-2) min-1 was obtained. Specific binding was eliminated by pretreatment of the membranes with trypsin. The concentration dependence for inhibition of binding with unlabeled PTH was identical to that for activation of adenylate cyclase in this membrane preparation, and binding was also inhibited by concentrations of calcium in the 0.5 to 2 mM range.
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PMID:Binding of tritiated bovine parathyroid hormone to plasma membranes from bovine kidney cortex. 1 29

The effects of bumetanide, a new potent diuretic, on net sodium transport of the isolated frog skin and on rat renal Na-K-ATPase were studied. A dose-related decrease in short-circuit current and potential difference with increased electrical resistance was observed when bumetanide was added to the corial side of the skin. Addition to the epithelial side resulted in enhanced net sodium transport with decreased electrical resistance. When applied to the corial side it abolished vasopressin- and aldosterone-stimulated transport. Present in the epithelial bath ouabain-inhibited transport was unaffected by this drug, while triamterene-induced inhibition of sodium transport was completely abolished. In vitro, no significant effects on Na-K-ATPase were noted. It is concluded that bumetanide shares properties of both furosemide and ethacrynic acid and excerts its effects on epithelial sodium transport by altering membrane permeability and possibly by inhibition of some step in the active transport mechanism for sodium.
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PMID:Effects of bumetanide on sodium transport of the isolated frog skin and on renal Na-K-ATPase. 13 61

1. Homogenates of bovine pituitary neural lobe tissue were subjected to differential centrifugation. Six subcellular fractions (I-VI) were obtained and the distribution among them of various cell organelles was studied by means of markers. Fraction II (800-3000 gav), the nerve-ending fraction (neurosecretosomes), contained sedimentable lactate dehydrogenase, hormone and a large proportion of the total Mg2 + +Na+ +K+-ATPase. 2. Lysis of the neurosecretosomes in hypotonic sucrose solutions led to loss of lactate dehydrogenase and vasopressin. 3. Centrifugation of the granule fraction (IV) on a sucrose gradient (1.3-2.0 M sucrose) gave a bimodal distribution of vasopressin. Purified neurosecretory granules were recovered from the denser band. Centrifugation on modified gradients (0.8-2.0 or 0.4-2.0 M sucrose) increased the yield of hormone in the denser band but the purity of the granules was decreased. 4. Considerable purification of the neurosecretosomes (fraction II) was achieved by "washing". Centrifugation of washed neurosecretosomes on sucrose density gradients led to the accumulation of all activities at a region between 1.4 and 1.5 M sucrose. 5. The distribution of Mg2+ +Na+ +K+-ATPase in centrifugal fractions indicated that the neurosecretosomes had been isolated in relatively high yield.
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PMID:Subcellular fractionation by centrifugation of homogenates of the neural lobe of the bovine pituitary gland: identification of different pools of hormone in the homogenate and isolation of neurosecretosomes. 14 Nov 84

Na+-K+-ATPase was inhibited by 1 times 10-4M ethacrynic acid and mercuderamide, and by 1 times 10-3M hydrochlorothiazide and furosemide. A modification of Gilman's (1970) protein displacement assay has been used to measure c-AMP levels in toad bladder epithelial cells. Vasopressin (50 mU/ml) caused c-AMP levels to rise from 4.27 to 9.27 pmol/mg protein. Ethacrynic acid had no effect on cellular c-AMP levels after 10 min exposure to the drug, but at 90 min caused a reduction of both basal and vasopressin stimulated levels. Furosemide caused an apparent rise in c-AMP levels, dilution ratio measurements indicated interference by this drug in the assay procedure, mecuderamide also caused substantial interference with the c-AMP assay. Hydrochlorothiazide had no effect on basal or hormone stimulated levels of c-AMP. It was concluded that the inhibition of sodium transport produced by ethacrynic acid in toad bladder is probably due to inhibition of adenylate cyclase, an effect not shared by other dieuretics.
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PMID:The effect of diuretics on Na+-K+-ATPase and c-AMP levels in toad bladder epithelial cells. 16 90

Free flow electrophoresis was employed to separate renal cortical plasma membranes into luminal (brush border microvilli) and contraluminal (basal-lateral membrane) fractions. During the separation adenylate cyclase activity was found to parallel the activity of Na+-K+-activated ATPase, an enzyme which is present in contraluminal but not in luminal membranes. In the basal-lateral membrane fraction the specific activities of adenylate cyclase and Na+-K+-activated ATPase were 4.4 and 4.6 times greater, respectively, than in the brush border fraction. The adenylate cyclase of the basal-lateral membrane fraction was specifically stimulated by parathyroid hormone which maximally increased enzyme activity eightfold. The biologically active (1-34) peptide fragment of paratyhroid hormone produced a 350% increase in adenylate cyclase activity. In contrast, calcitonin, epinephrine and vasopressin maximally stimulated the enzyme by only 55, 35 and 30%, respectively. These results indicate that adenylate cyclase, specifically stimulated by parathyroid hormone, is distributed preferentially in the contraluminal region of the plasma membrane of renal cortical epithelial cells.
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PMID:Distribution of parathyroid hormone-stimulated adenylate cyclase in plasma membranes of cells of the kidney cortex. 17 37

Two types of plasma membrane were purified from canine distal renal medulla by the techniques of differential and zonal density-gradient centrifugation followed by free-flow electrophoresis. One group of plasma membranes was identified as basal-laterally derived based on a 30-fold enrichment of Na-K-ATPase, a 20-fold enrichment of vasopressin-stimulated adenylate cyclase, and a 33-fold enrichment of [3H]vasopressin binding sites. The second type of plasma membrane was free of these markers, but had a cholesterol and phospholipid composition similar to them. Alkaline phosphatase also had a similar distribution in the two fractions. This lighter membrane fraction contained a membrane-bound cyclic AMP-dependent protein kinase as well as substrate for this kinase. In addition there was a 26-fold enrichment of specific activity of an anion (SO32-)-activated ATPase which was insensitive to mitochondrial ATPase inhibitor protein, in contrast to the mitochondrial fraction of the tissue. Based on the relative preponderance of collecting duct tissue in the distal medulla and the yield of membrane protein, these membranes are tentatively identified as containing apical membranes of the collecting duct.
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PMID:Purification of distinct plasma membranes from canine renal medulla. 20 99

Bovine neurohypophyses were fractionated by differential and density gradient ultracentrifugation and the Ca-2+ uptake and ATPase activities in the microsomal, mitochondrial and secretory granule fractions were studied. The microsomal and mitochondrial fractions accumulated Ca-2+ in the presence of ATP. The accumulation by the latter per mg protein was at least twice as large as by the former. This Ca2+ accumulation was accompanied by liberation of inorganic phosphate (Pi). In the presence of sodium azide (2 mM) Ca-2+ uptake and Pi liberation were inhibited in the mitochondrial, but not in the microsomal fraction. Further studies of the microsomal fractions revealed that the ATP-dependent Ca-2+ uptake and Pi liberation activities were temperature and pH-dependent and required Mg-2+. Both activities were stimulated by very low concentrations of Ca-2+ (1-10 muM) and were inhibited by EGTA (2 mM). N-ethylmaleimide (2 mM) inhibited both the Ca-2+ uptake and ATPase activities of the microsomal fraction. These results suggest the presence of a membrane ATPase that is stimulated by both Ca-2+ and Mg-2+. It is suggested that the observed Ca-2+ uptake activities are involved in maintaining a low axoplasmic free Ca-2+ concentration, thus playing an important role in the release mechanism of vasopressin by the neurosecretory terminals.
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PMID:Adenosine triphosphate dependent calcium uptake by subcellular fractions from bovine neurohypophyses. 23 61

Ethanol, like other anesthetics, has been reported to interfere with active Na+ transport in living membranes. In an attempt to elucidate the mechanism by which ethanol exerts this action, we tested in the toad bladder membrane: 1) the effect of ethanol on active Na+ transport, 2) the interaction of ethanol with vasopressin on Na+ transport, and 3) the effect of ethanol on passive Na+ flux. We found that, a) 1-500 microgram/ml of ethanol stimulated, and 10,000 microgram/ml depressed active Na+ transport; b) the combined effect of stimulating concentrations of ethanol and vasopressin, although suggestive of a positive interaction, might have arisen by chance (p = 0.08); c) depressant concentrations of ethanol failed to suppress the stimulation by vasopressin; and d) passive Na+ flux in bladders treated with ouabain and ethacrynic acid was not affected by ethanol (1-100 microgram/ml). These results indicate that ethanol in concentrations ranging from 1 to 10,000 microgram/ml does not block ATP/ATPase Na+ pump but apparently exerts a dose-dependent, stimulant-depressant effect on Na+ channels in the membrane.
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PMID:Ethanol effects on active and passive Na+ flux in toad bladder. 41 65


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