Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of Ca++ mobilizing agonists arginine vasopressin and phenylephrine on Na+/H+ exchange was studied in freshly isolated hepatocytes and isolated perfused rat livers. The activity of Na+/H+ exchange was determined from the rate of H+ efflux, 22Na uptake and pHi recovery. Arginine vasopressin and phenylephrine stimulated H+ efflux and 22Na uptake in isolated rat hepatocytes and increased the rate of pHi recovery from acid-loaded hepatocytes. These effects were inhibited by amiloride. Arginine vasopressin- and phenylephrine-induced increases in H+ efflux were also dependent on extracellular Na+. Arginine vasopressin- and phenylephrine-induced increases in intracellular Ca++ concentration, H+ efflux, 22Na uptake and intracellular pH recovery were decreased in hepatocytes preloaded with the Ca(++)-buffering agent [bis-(2-amino-5-methylphenoxy)-ethane-N,N,N',N'-tetraacetic acid] (MAPTA). Na+/H+ exchange-dependent intracellular pH recovery from cytosolic acidification was stimulated by thapsigargin, which increases intracellular calcium concentration by inhibiting endoplasmic reticulum Ca++ ATPase. Arginine vasopressin- and phenylephrine-induced increases in intracellular pH recovery were not dependent on extracellular Ca++ and were inhibited by calmidazolium, a calmodulin inhibitor. Arginine vasopressin and phenylephrine also increased H+ efflux in the absence but not in the presence of amiloride in perfused rat livers without affecting biliary HCO3- excretion. These results indicate that arginine vasopressin and phenylephrine activate Na+/H+ exchange in rat hepatocytes, an effect mediated in part by intracellular Ca++ and calmodulin kinase. Furthermore, sinusoidal Na+/H+ exchange does not appear to be involved in biliary HCO3- excretion.
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PMID:Intracellular calcium-mediated activation of hepatic Na+/H+ exchange by arginine vasopressin and phenylephrine. 130 63

Transgenic mice for the promoter sequence of bovine arginine vasopressin (AVP) gene fused to large SV40 T-antigen coding sequence develop pituitary tumors and insulin-producing pancreatic tumors. In order to establish the cellular composition of the pituitary tumors, histological, immunocytochemical, in situ hybridization, and electron microscopic technics were applied. Pituitary anterior lobe tumors were identified in 10 out of 14 glands examined. In 2 of these cases, intermediate lobe tumors were also found. The anterior lobe tumors contained a variable number of GH immunoreactive cells. In situ hybridization performed in 7 cases revealed a diffuse distribution of GH messenger RNA over all tumor cells. Ultrastructurally, the tumors contained undifferentiated cells with very small secretory granules and rare cells showing some resemblance to somatotrophs. The results indicate that these pituitary tumors are composed of undifferentiated somatotrophs. The presence of a few PRL immunoreactive cells in four tumors and scattered TSH immunoreactive cells in two tumors supports the view that somatotrophs have the potential to produce PRL and TSH. The intermediate lobe tumors were immunoreactive for ACTH and intensely positive for POMC mRNA. In the nontumorous adenohypophyses, no hyperplasia of any cell type was noted. Several GH immunoreactive cells exhibited pleomorphic, giant nuclei and mitoses. In conclusion, the majority of transgenic mice for AVP/large T-antigen develop pituitary tumors originating in and composed of somatotrophs. Less frequently, intermediary lobe tumors were present as well. AVP/SV40 transgenic mice provide a unique experimental model for somatotroph tumors that are neither preceded by, nor associated with somatotroph hyperplasia.
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PMID:Morphology of adenohypophysial tumors in mice transgenic for vasopressin-SV40 hybrid oncogene. 131 26

The effect of inhibition of Na+/K(+)-ATPase by ouabain on the arginine vasopressin (AVP)-induced increase in intracellular Na+ concentration [( Na+]i) was examined in cultured rat vascular smooth muscle cells (VSMC) by the direct measurement of [Na+]i using a fluorescent indicator dye. AVP at a concentration of 1 x 10(-9) M or higher increased [Na+]i in a dose-dependent manner in cultured rat VSMC. The preincubation of cells with 1 x 10(-4) M ouabain for 1 hr at 37 degrees C did not affect the basal [Na+]i but enhanced the 1 x 10(-6) M AVP-induced increase in [Na+]i. The preincubation was not necessary because similar results were obtained after the simultaneous administration of AVP and ouabain. The treatment with ouabain did not affect the intracellular pH changes induced by AVP. These results therefore indicate that the inhibition of Na+/K(+)-ATPase enhances the AVP-induced increase in [Na+]i by decreasing cellular Na+ efflux in cultured rat VSMC.
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PMID:Effect of inhibition of Na+/K(+)-ATPase on the vasopressin-induced increase in intracellular Na+ concentration in vascular smooth muscle cells. 164 67

The purpose of this experiment is to study the role of arginine vasopressin (AVP) in acute cerebral ischemic edema in Mongolian gerbils. The results show that intracerebroventricular injection (ICV) of AVP exacerbates acute ischemic brain edema, while ICV of AVP antiserum significantly decreases the ischemic brain edema. Nimodipine (calcium antagonist) cannot block this role of AVP in brain edema. In addition, the cortical Na(+)-K+ ATPase activity is significantly decreased, while the cAMP content of ischemic cortex and hypothalamus and the cGMP content of the hypothalamus are markedly increased after AVP ICV. These suggest that AVP may play an important role in the pathophysiologic process of ischemic brain edema by inhibiting the Na(+)-K+ ATPase activity of the cerebral cell membrane and the AVP receptors mediated by cAMP and cGMP.
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PMID:Mechanism of action of arginine vasopressin on acute ischemic brain edema. 165 29

Primary cultures of renal rabbit proximal tubule cells were initiated from a pure suspension of proximal tubule fragments. Proximal tubule cells were grown in a hormone-supplemented, serum-free medium containing low concentrations of antibiotics. Confluent monolayers exhibited multicellular dome formation, indicating the presence of transepithelial solute and water transport. Ultrastructural examination revealed a monolayer of polarized epithelial cells with tight junctions and sparse membraneous microvilli facing the culture medium. Time course biochemical characterization was performed using a palette of 12 enzymes, representative of important metabolic functions or pathways. Brush-border-associated enzymes (gamma-glutamyl transpeptidase and alanine aminopeptidase) were moderately reduced throughout the culture whereas alkaline phosphatase was markedly decreased at confluency. Mitochondrial and lysosomal marker enzymes were well preserved over the culture period. Glutathione-S-transferase activity remained stable during the 16-day culture period investigated. Glycolysis enzyme activities (lactate dehydrogenase and hexokinase) were enhanced, as a function of culture age. Na(+)-K(+)-ATPase activity rise was concomitant with the increase of glycolysis marker enzymes. In contrast, the gluconeogenesis marker enzyme, glucose-6-phosphatase, fell dramatically to reach a low level equivalent to 4% of the activity measured in isolated proximal tubules. Primary cultures exhibited several differentiated functions of the proximal tubule cell: (a) PTH alone was able to induce a significant stimulation of adenylate cyclase activity, unlike isoproterenol, thyrocalcitonin, and arginine vasopressin, and (b) sodium-dependent alpha-methylglucoside (AMG) transport was detected. This AMG uptake was selectively inhibited by phlorizin (5 X 10(-3) M), which is a competitive inhibitor of glucose uptake at the apical membrane. Complete characterization made it possible to investigate hitherto unexplored aspects of in vitro cultured proximal tubule cells. This primary culture model could provide a useful and reliable tool to investigate in vitro renal proximal tubule function, under normal conditions or after a drug-induced toxicity.
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PMID:Biochemical, functional, and morphological characterization of a primary culture of rabbit proximal tubule cells. 167

We recently demonstrated that renal synthesis of cytochrome P-450-dependent arachidonic acid (AA) metabolites is increased in spontaneously hypertensive rats (SHR) during the rapid elevation of blood pressure. In this study, the chemical identity of these metabolites is described, and the structural analysis together with differential susceptibility to antibodies suggested that they are derived from at least two different cytochrome P-450 isozymes: 1) the epoxygenase that metabolizes AA mainly to 11,12-epoxyeicosatrienoic acid (EET), which is further hydrolyzed to 11,12-dihydroxyeicosatrienoic acid (DHT) and 2) omega/omega-1 hydroxylase(s) that generate the 20-hydroxyeicosatetraenoic acid (HETE) and 19-HETE, respectively. Their production and release from the isolated kidney was activated by arginine vasopressin and inhibited by cytochrome P-450 enzyme inhibitors. The formation of these metabolites in SHR or WKY cortical microsomes was age dependent. The production rates of EET, DHT, and 19-HETE increased from fetal to 9 wk of age by 3-, 6- and 4-fold, respectively, whereas that of 20-HETE increased by 27-fold. The omega/omega-1 hydroxylase activities were significantly higher in SHR, whereas epoxygenase activity (sum of EET and DHT production) demonstrated no differences between the two strains at any age group tested, although the amount of EET vs. DHT in a given age was significantly different. Since these metabolites have a wide and contrasting spectrum of biological and renal effects (vasodilation and vasoconstriction, inhibition and stimulation of Na(+)-K(+)-ATPase), their relative production rates at a given age may influence not only renal hemodynamics and salt and water balance but also pro- and antihypertensive mechanisms in SHR.
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PMID:Age-related changes in renal cytochrome P-450 arachidonic acid metabolism in spontaneously hypertensive rats. 173

Prostacyclin (PGI2) did not alter the basal perfusion pressure in the isolated rat mesenteric arteries perfused with Krebs' solution, but produced a biphasic effect in arteries preconstricted with norepinephrine or arginine vasopressin: constriction, then prolonged dilation. Both these components of PGI2 effect were diminished in arteries denuded of their endothelia by a 10 min perfusion with distilled water or p-bromophenacyl bromide (10 microM). The present study elucidates the mechanism of these PGI2 actions. Indomethacin (0.28 microM) SQ 29548 (1 microM, thromboxane A2 receptor antagonist), saralasin (1 microM, angiotensin II receptor antagonist) or the free radical scavengers, superoxide dismutase (60 U/ml) and catalase (40 U/ml) did not inhibit the initial vasoconstriction, suggesting it was not mediated through endothelially generated thromboxane A2, angiotensin II or oxygen-derived free radicals. However, ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (50 microM; Ca++ chelating agent), 8-(diethyl-amino)octyl 3,4,5-trimethoxy benzoate (10 microM; intracellular Ca++ antagonist), or neomycin (5 mM; phospholipase-C inhibitor) abolished the vasoconstriction. Ouabain (0.5 mM) did not affect the vasodilation, but perfusion with excess (50 mM) or 0 K+ Krebs' solution abolished it, suggesting this PGI2 action involves changes in membrane K+ conductance via a mechanism independent of Na+/K+ adenosine triphosphatase. Vasodilation evoked by BRL 34915 (K+ channel activator) was similarly attenuated under these conditions, but not by ouabain. Furthermore, procaine (1 mM; nonspecific K+ channel inhibitor), but not apamin (0.5 microM) or tetraethylammonium (10 mM) blocked PGI2- and BRL 34915-induced vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of vascular actions of prostacyclin in the rat isolated perfused mesenteric arteries. 210 93

12(R)-HETE [12(R)-hydroxy-5, 8, 10, 14 eicosatetraenoic acid] is one of the major arachidonic acid metabolites produced by microsomal cytochrome P450 of the corneal epithelium. This metabolite is a potent inhibitor of Na(+)-K(+)-ATPase activity in several tissues. We investigated endogenous production of 12(R)-HETE in the rabbit corneal epithelium. Incubation of corneal epithelial sheets (prelabeled with 14C-arachidonic acid) with arginine vasopressin resulted in the production of radioactive 12(R)-HETE suggesting its formation from endogenously labeled-arachidonic acid. The maximal response was obtained with 1 microM arginine vasopressin and represents a 15-fold increase in 12(R)-HETE formation compared with that of control tissues. Stimulation of 14C-arachidonic acid release with a detergent, digitonin, also resulted in endogenous 12(R)-HETE formation. Analysis of the incubation media following digitonin treatment of prelabeled corneal epithelial sheets revealed that 12(R)-HETE production was maximal at 20 microM digitonin, a 17-fold increase over control values. This study is the first to describe hormonal and traumatic stimulation of 12(R)-HETE formation from endogenously labeled arachidonic acid in intact corneal tissues. This study demonstrates that the formation of this Na(+)-K(+)-ATPase inhibitor can be modulated by physiological and pathophysiological regulation.
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PMID:Hormonal stimulation of 12(R)-HETE, a cytochrome P450 arachidonic acid metabolite in the rabbit cornea. 211 38

The present study was undertaken to examine the cellular interaction between a Na+/K(+)-ATPase inhibitor, ouabain, and arginine vasopressin (AVP) in rat vascular smooth muscle cells (VSMC) in culture. Preincubation with 10(-5) M ouabain for 60 min increased basal cytosolic free Ca2+ [( Ca2+]i) concentration and intracellular 45Ca2+ uptake. Ouabain, however, did not affect basal 45Ca2+ efflux or AVP-stimulated 45Ca2+ efflux. As assessed by cell shape change, preincubation with 10(-5) M ouabain for 60 min also enhanced the sustained cellular contractile effect of a submaximal (10(-8) M AVP, 21.5% vs. 30.5%, P less than 0.01) but not maximal dose of 10(-6) M AVP. Preincubation with 10(-5) M ouabain for 60 min did not change AVP-induced V1-specific surface receptor binding or AVP-induced inositol phosphate production but did however potentiate the mobilization of [Ca2+]i induced by a submaximal (10(-8) M AVP, 301 vs. 385 nM, P less than 0.01) but not a maximal dose of AVP. These effects of ouabain on the mobilization of [Ca2+]i were abolished by incubation in Ca2(+)-free buffer or 5 X 10(-5) M verapamil. Ouabain (10(-5) M) also enhanced the sustained cellular contractile effect of a direct protein kinase C activator, phorbol 12-myristate 13-acetate. The present results therefore indicate that the inhibition of Na+/K(+)-ATPase may enhance the vascular action of AVP, and perhaps other vasoconstrictors, by increasing the AVP-induced mobilization of [Ca2+]i and by potentiating the activity of protein kinase C stimulated by AVP through enhancing basal and AVP-stimulated cellular Ca2+ uptake.
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PMID:Effect of inhibition of Na+/K(+)-adenosine triphosphatase on vascular action of vasopressin. 217 Apr 49

In previous studies, we have demonstrated that 1-10 fmol arginine vasopressin (AVP)/l maximally stimulates the activity of the enzyme Na+/K(+)-ATPase in the rat renal medullary thick ascending limb (MTAL) of Henle's loop after 4 or 10 min of stimulation when measured using a cytochemical bioassay. We have tested the hypothesis that this stimulation is mediated by the V2 receptor in the MTAL. A cytochemical bioassay was used to investigate the effect of specific V1 and V2/V1 antagonists and a synthetic V2 agonist [1-deamino,8-D-arginine]-vasopressin (dDAVP), on the activity of Na+/K(+)-ATPase. There was no effect of the V1 antagonist (1 fmol-1 mumol/l) in inhibiting the activity of Na+/K(+)-ATPase stimulated by 1 fmol AVP/l. In contrast, 100 pmol of the V2/V1 antagonist/l significantly (P less than 0.001) inhibited the stimulation of Na+/K(+)-ATPase activity by 1 fmol AVP/l from 55.5 +/- 4.3 (S.E.M.) to 31.9 +/- 1.6 mean integrated extinction (MIE) after 4 min of stimulation and from 67.0 +/- 3.2 to 36.9 +/- 0.7 MIE after 10 min of stimulation. Similarly, the stimulation of Na+/K(+)-ATPase by 10 fmol dDAVP/l was inhibited by the V2/V1 antagonist from 55.1 +/- 1.0 to 26.1 +/- 0.5 MIE after 4 min of stimulation. We conclude that the stimulation of Na+/K(+)-ATPase by AVP is mediated by the V2 receptor in the rat renal MTAL.
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PMID:Stimulation of rat renal medullary Na+/K(+)-ATPase by arginine vasopressin is mediated by the V2 receptor. 217 53


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