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)

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

Luminal brush border and contraluminal basal-lateral segments of the plasma membrane from the same kidney cortex were prepared. The brush border membrane preparation was enriched in trehalase and gamma-glutamyltranspeptidase, whereas the basal-lateral membrane preparation was enriched in (Na+ + K+1)-ATPase. However, the specific activity of (Na+ + K+)-ATPase in brush border membranes also increased relative to that in the crude plasma membrane fraction, suggesting that (Na+ + K+)-ATPase may be an intrinsic constituent of the renal brush border membrane in addition to being prevalent in the basal-lateral membrane. Adenylate cyclase had the same distribution pattern as (Na+ + K+)-ATPase, i.e. higher specific activity in basal-lateral membranes and present in brush border membranes. Adenylate cyclase in both membrane preparations was stimulated by parathyroid hormone, calcitonin, epinephrine, prostaglandins and 5'-guanylylimidodiphosphate. When the agonists were used in combination enhancements were additive. In contrast to the distribution of adenylate cyclase, guanylate cyclase was found in the cytosol and in basal-lateral membranes with a maximal specific activity (NaN3 plus Triton X-100) 10-fold that in brush border membranes. ATP enhanced guanylate cyclase activity only in basal-lateral membranes. It is proposed that guanylate cyclase, in addition to (Na+ + K+)-ATPase, be used as an enzyme "marker" for the renal basal-lateral membrane.
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PMID:Preparation of renal cortex basal-lateral and bursh border membranes. Localization of adenylate cyclase and guanylate cyclase activities. 1 97

The hormonal responsiveness of plasma membrane-bound enzymes (Na-+-K-+)-ATPase and adenylate cyclase has been investigated in normal and regenerating rat liver. (Na-+-K-+)-ATPase basal activity is not affected by surgery and only slightly affected by partial hepatectomy; its response to epinephrine and cyclic AMP is decreased only 15 h after hepatectomy. Adenylate cyclase activity of plasma membranes from untreated animals is stimulated by parathyroid hormone and thyroxine; partial hepatectomy increased basal activity as well as the stimulation exerted by the aforementioned hormones, when glucagon and epinephrine sensitivity is essentially unaltered.
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PMID:Hormone responsiveness of plasma membrane-bound enzymes in normal and regenerating rat liver. 12 2

Dichloromethylene diphosphonate (Cl2MDP) was given at doses of 4 mg/kg and 10 mg/kg daily for 7 days to adult thyroparathyroidectomized rats fed a low calcium diet. Primary metaphyseal trabeculae in Cl2MDP-treated rats were more numerous and longer than in controls. The light and electron microscopic appearance of osteoblasts, osteocytes and osteoclasts were unaltered by Cl2MDP. Bone alkaline phosphatase was significantly elevated in rats given Cl2MDP but adenosine triphosphatase activity was unchanged. Bone fat-free weight, fat-free minus ash weight, and bone calcium and phosphorus concentration were reduced significantly in rats given 10 mg/kg Cl2MDP compared to controls. Bone magnesium concentration was significantly elevated in rats given 10 mg/kg Cl2MDP. Serum calcium and phosphorus concentration were lower in Cl2MDP-treated rats. These results suggest that Cl2MDP is capable of altering bone remodeling, enzyme activity and mineral content, without significantly altering bone cell morphology, independent of the effects of parathyroid hormone, calcitonin, and dietary calcium.
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PMID:Effect of dichloromethylene diphosphonate on morphology, enzyme activity, and ash content of bones of thyroparathyroidectomized rats. 14 84

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

The effect of parathyroid hormone (PTH) on the action potential of myocardium cells under conditions of the oubain--reduced activity of transport ATPase tells in reduced duration of the plateau and in increased amplitude of evoked potentials. The form of the AP alters on administration of the hormone against the background of expressed activity of the cardiac glycoside. The increase in the AP amplitude and the appearance of the "peak"preseding the plateau phase due to the hormone administration seem to be entailed by an action of the hormone upon the transport of sodium ions and activity of the membrane Na, K--dependent ATPase. The effect of PTH upon the contractile activity of the myocardium cells under the oubain influence becomes inverse: instead of a decrease in the contractions amplitude the hormone administration entails an elongation of the "therapeutic" phase of oubain action. The elongation also occurs after a preliminary work of the myocardium strip in the PTH solution. The effect seems to follow the increase of amount of calcium in the cell under the hormone effect.
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PMID:[Effect of parathyroid hormone on the myocardium in the presence of ouabain-induced reduced membrane ATPase activity]. 22 26

The activity of Na(+)-K+ ATPase of pancreatic islets modulates their insulin secretion. The study presented here examined the activity of this enzyme in pancreatic islets of chronic renal failure (CRF) rats in an effort to further delineate the mechanisms of impaired insulin secretion in CRF. The Vmax of Na(+)-K+ ATPase, but not its Km, and the ATP content are significantly reduced in islets of CRF rats that have elevated levels of parathyroid hormone (PTH). These derangements are prevented by prior parathyroidectomy of CRF rats (low blood levels of PTH) or by their treatment with the calcium channel blocker verapamil; these latter rats have sustained elevation of blood levels of PTH. The data indicate that the chronic excess blood levels of PTH in CRF initiates events (augmented entry of calcium) that lead to the reduction in ATP content and in Vmax of Na(+)-K+ ATPase of pancreatic islets. Reducing the blood levels of PTH by parathyroidectomy or blocking the action of PTH on calcium entry into cells by verapamil prevents these derangements. The results suggest that chronic inhibition of Na(+)-K+ ATPase may participate in the processes underlying the impaired insulin secretion in CRF.
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PMID:Reduced activity of Na(+)-K+ ATPase of pancreatic islets in chronic renal failure: role of secondary hyperparathyroidism. 132 Sep 48

Renal cortex homogenates from aged (greater than 5 y) rabbits showed decreased specific activities of brush border membrane enzymes compared to those from control young (6 m) rabbits but the specific enzyme activities of basolateral membrane, endoplasmic reticulum and mitochondria did not differ between the two groups. The stimulatory effects of parathyroid hormone (PTH) on the Ca(2+)-pump enzyme [(Ca(2+)+Mg2+)-ATPase] activity in kidney cortex homogenates were markedly less in aged rabbits, but the effect of cAMP on this enzyme activity was similar. Moreover, the production of cAMP induced by PTH was markedly less in the renal cortex homogenates from aged rabbits. From these results, we have proposed the following mechanism; aging--decrease in the response of cAMP to PTH in renal cortex--decrease in the stimulatory effect of PTH via cAMP on the Ca(2+)-pump enzyme--decreased reabsorption of Ca2+ from ureter--increased urinary Ca2+ secretion. This pathway may contribute to the worsening of senile osteoporosis.
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PMID:Effects of aging on renal response to parathyroid hormone in vitro. 135 71

Epoxygenase and omega- and omega-1-hydroxylases are the major cytochrome P-450-arachidonate (P-450-AA) metabolizing enzymes in renal tissues. We measured P-450-AA metabolism in single nephron segments and determined the tubular localization of this activity in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Formation of 20-hydroxyeicosatetraenoic acid (20-HETE), the product of AA omega-hydroxylase was specifically localized in the entire proximal tubules (S1, S2, and S3 segments), whereas formation of 19-HETE, the product of omega-1-hydroxylase and epoxyeicosatrienoic acids (EETs), products of AA epoxygenase, was demonstrable throughout the tubule. Although distribution patterns were similar in SHR and WKY, formation of 19- and 20-HETE in the proximal tubules was higher in SHR, whereas the formation of EETs was not different between the two strains. In the proximal tubules, angiotensin II (ANG II) significantly stimulated epoxygenase activity (EETs formation), whereas parathyroid hormone (PTH) and epidermal growth factor (EGF) had no effect on epoxygenase but significantly stimulated omega-hydroxylase activity (20-HETE formation). Because P-450-AA metabolites have a wide and contrasting spectrum of biological and renal effects, from vasodilation to vasoconstriction and from inhibition to stimulation of Na(+)-K(+)-adenosinetriphosphatase, their localization to the specific nephron segments and differential stimulation of their formation by ANG II, PTH, and EGF may contribute not only to renal hemodynamics and blood pressure regulation but also to the regulation of renal sodium and water balance.
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PMID:Renal cytochrome P-450-arachidonic acid metabolism: localization and hormonal regulation in SHR. 156 72

We studied the influence of aging on the stimulatory effect of parathyroid hormone (PTH) to (Ca2+ + Mg2+)-ATPase activity of rabbit renal basolateral membrane (BLM). Stimulated by PTH, (Ca2+ + Mg2+)-ATPase activity of BLM from aged rabbits was lower than those from young rabbits. However, the stimulatory effect of cyclic AMP (cAMP) showed no differences in terms of (Ca2+ + Mg2+)-ATPase activity in BLM from aged and young rabbits. As cAMP production in BLM caused by PTH stimulation was not measured, it is unclear whether cAMP production is different in BLM from young and aged rabbits. From these results, we concluded that in BLM from aged rabbit, the lower effect of PTH on (Ca2+ + Mg2+)-ATPase is due to lower production of cAMP or some other disorder of the PTH signal transduction mechanism. As (Ca2+ + Mg2+)-pump plays an important role in Ca2+ reabsorption in kidney, its lower activity in aged rabbit may be one reason for aberration of renal calcium handling.
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PMID:[The influence of aging on parathyroid hormone-induced enhancement in (Ca2+ + Mg2+)-ATPase activity of rabbit renal basolateral membrane]. 165 68


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