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)

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 effects of acute and chronic administration of D-Galactosamine (GalN), Ethanol and Phenobarbital were investigated on the activities of lysosomal enzymes, i.e.; acid phosphatase, beta-glucuronidase and n-acetyl-beta-glucosaminidase, and others such as gamma-GTP and adenosine triphosphatase. The histochemical distribution of gamma-GTP in the liver was also studied on biopsy specimens from patients with chronic hepatitis, and gamma-GTP levels in the serum of patients receiving drugs inductable of hepatic microsomal enzymes. 1) After a single intraperitoneal injection of GalN, the lysosomal enzyme activities were lowered in the necrotic areas, but raised in the perinecrotic areas, the proliferative Kupffer cells and intra- and/or extra-cellular eosine bodies. 2) gamma-GTP activities in rat liver after chronic administration of GalN were markedly increased in bile canalicular membrane of periportal parenchymal cells, the epithelium of bile duct and ductules, and som inflammatory cells of portal fields. Levels of serum gamma-GTP were also elevated. On histochemical studies with biopsy specimens from patients with chronic active hepatitis showing elevated gamma-GTP activity, the activity was revealed a similar localization to GalN-treated rats. These data suggested that the increased activities might be reflected on the active stage in chronic hepatitis. 3) Chronic ethanol treatment in rats induced clearly-stained lysosomes varied in size, especially large-sized. The activities of hepatic gamma-GTP were slightly increased in the bile canalicular membrane of periportal parenchymal cells and the epithelium of proliferative bile ductules. 4) It has been shown by histochemical and biochemical techniques that hepatic gamma-GTP activity was increased after phenobarbital administration in rats. A significant rise in serum gamma-GTP was observed in patients on long-term treatment with anti-epileptic drugs. These data indicated that the increased activities of serum gamma-GTP might be accompanied with induction of hepatic microsomal drug-metabolizing enzymes.
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PMID:[Clinical and experimental histochemical studies on the activities of liver lysosomal enzymes and gamma-glutamyl transpeptidase (gamma-GTP) (author's transl)]. 3 25

The effects of deoxycholate, taurocholate and cholate on transport and mucosal ATPase activity have been investigated in the rat jejunum in vivo using closed-loop and perfusion techniques. In the closed-loops, 5 mM deoxycholate selectively inactivated (Na+ + K+)-ATPase, and net secretion of Na+ induced by 2.5 mM deoxycholate was due to reduced lumen to plasma flux of the ion; deoxycholate (2.5 mM) produced marked inhibition of 3-0-methylglucose transport. Luminal disappearance rates of deoxycholate (60.5 plus or minus 2.9% per g wet st of gut) greatly exceeded those of taurocholate (4.3 plus or minus 1.0). In the perfusion studies 1 mM deoxycholate induced net secretion of water, Na+ and C1-, and inhibited active glucose transport; concomitantly "total" ATPase, (Na+ + K+)-ATPase, and Mg-2+-ATPase were inhibited. At higher concentrations (5 mM) deoxycholate stimulated Mg-2+-ATPase activity. Taurocholate and cholate at 1mM had no effect on transport of (Na+ + K+)-ATPase. Mucosal lactase, sucrase and maltase activities were not affected by 1 mM deoxycholate, taurocholate or cholate. These results suggest that deoxycholate inhibits sodium-coupled glucose transport by inhibition of (Na+ + K+)-ATPase at the lateral and basal membranes of the epithelial cell, rather than from an effect at the brush-border membrane level.
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PMID:A comparative study on the effects of different bile salts on mucosal ATPase and transport in the rat jejunum in vivo. 12 87

This paper reviews the principal effects of phenobarbital on biliary function. Phenobarbital administration is followed by an increase in bile flow. This is mainly due to an increase in the bile salt-independent fraction of canalicular bile flow possibly through an increase in canilicular Na+-K+ ATPase activity. In addition, bile salt excretion may be increased. This effect of barbiturates on choleresis appears to be independent of microsomal enzyme induction. Barbiturates increase the uptake, storage and excretion of various dyes, for example sulfobromophthalein. Phenobarbital increases bilirubin clearance by the liver; it enhances bilirubin-UDP-glucuronyl transferase activity; whether the influence on bilirubin clearance is related to the effect on the enzyme is unknown. The influence of phenobarbital on biliary lipids is markedly different from one species to the other. In the rhesus monkey and in the rat, the relative concentration of cholesterol is decreased; in the hamster it is increased, and in man it appears largely unaffected. These effects of phenobarbital have been utilized in the treatment of chronic unconjugated hyperbilirubinemia and of certain cholestatic syndromes. Phenobarbital alone has been useful, so far, in the treatment of cholesterol gallstones.
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PMID:Barbituates and biliary function. 12 85

Since phenobarbital administration produces a profound increase in bile flow without changing bile acid secretion, we examined whether this drug increases the activity of hepatic sodium-potassium-activated ATPase [Na+-K+)-ATPase], the postulated regulating enzyme in the secretion of bile salt independent bile flow. After freeze-thawing to increase substrate accessibility, (Na+-K+) ATPase activity was determined by ouabain inhibition of total ATPase activity. Its activity was highest in isolated liver surface membrane fractions enriched in bile canalicult. Phenobarbital administration significatly increased (Na+-K+)-ATPase activity in both liver surface membrane fractions as well as liver homogenates. This enhanced activity is apparently selective for other membrane phosphatases and the enzyme activity in other tissues is either unaltered or decreased. Kinetic analysis of (Ka+-K+)-ATPase indicates that phenobarbital treatment increased maximum velocity and half-maximum activation constant was unchanged, consistent with activation of latent molecules or an increased number of enzyme molecules. The latter process seems more likely because cycloheximide prevented phenobarbital induction and activators were not demonstrated in vitro. Examination of the full time course of phenobarbital induction to determine whether phenobarbital increased synthesis or decreased degradation was consistent with increased synthesis since the apparent degradation rates were similar with or without phenobarbital treatment. The apparent half-life for (Na+-K+)-ATPase was estimated to be approximately 2.5 days, consistent with liver surface membrane protein turnover. The correlation of changes in bile flow with (Na+-K+)-ATPase was examined under several experimental situations. Phenobarbital caused a parallel increase in each during the 1st 2 days of greatment: thereafter other factors become rate limiting for flow, since enzyme activity doesn't reach a new steady state until 4-days. Consistent with increased sodium-potassium exchange, bile sodium was unchanged while potasium concentrations were significantly reduced. Changes in both bile flow and (Na+-K+)-ATPase induced by phenobarbital are independent of thyroid hormone. These studies support the postulate that (Na+-K+)-ATPase is an important factor in regulation of bile flow. In addition, phenobarbital enhancement of both bile flow and (Na+-K+)-ATPase is dependent upon de novo protein synthesis.
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PMID:Stimulation of hepatic sodium and potassium-activated adenosine triphosphatase activity by phenobarbital. Its possible role in regulation of bile flow. 19 64

Luminal (brush border) and antiluminal (basal-lateral) membranes were isolated from canine renal cortex. The enzyme marker for luminal membrane, alkaline phosphatase was enhanced 19-fold and the antiluminal enzyme marker, (Na+ + K+)-ATPase, was enhanced 22-fold in their respective membrane preparation, while the amount of cross contamination was minimal. Contamination of these preparations by enzyme markers for lysosomes, endoplasmic reticulum and mitochondria was also low. Routinely, more than 50 mg membrane protein was isolated for each membrane. Electron micrographs showed that the membranes were uniform in size, appearance, and vesicular in nature. An examination of the orientation of these membranes showed that 76.5% of the antiluminal membranes and 86% of the luminal membranes were right-side out.
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PMID:Isolation of luminal and antiluminal membranes from dog kidney cortex. 22 Oct 18

Previous studies suggest that enhancement of rubidium tracer (86Rb) lumen-to-bath efflux following removal of luminal Na is mediated in part by a Ba-insensitive pathway. To determine the role of a primary active K pump in this response, we examined the action of known inhibitors of H-K-ATPase (Sch 28080) and Na-K-ATPase (ouabain) on the 86Rb lumen-to-bath efflux coefficient (KRb). Luminal Sch 28080 (10 microM) significantly reduced KRb by 39 +/- 8.0% (P less than 0.05), whereas luminal ouabain (0.1 mM) reduced KRb by 10 +/- 14% (P = not significant), suggesting that a luminal H-K-ATPase mediates Rb efflux. To examine whether H-K-ATPase mediates Rb in KRb following removal of luminal Na, additional experiments were conducted to examine the effect of Sch 28080 on KRb in the presence and the absence of luminal Na. In the presence of luminal Na, 10 microM Sch 28080 reduced KRb by 15 +/- 5.0%. However, in the absence of luminal Na, 10 microM Sch 28080 decreased KRb by 48 +/- 8.2%. The percentage inhibition of KRb by Sch 28080 was significantly greater in the absence of luminal Na than in its presence (P less than 0.01), suggesting that the enhancement of KRb following removal of luminal Na is mediated in part by an H-K-ATPase pathway. In either case transepithelial voltage was not significantly altered. In contrast to the lack of effect of luminal ouabain, addition of 0.1 mM ouabain to the bath increased KRb (69.8 +/- 11.1 vs. 95.9 +/- 18.7 nm/s, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:H-K-ATPase enhancement of Rb efflux by cortical collecting duct. 132 55

To examine the pathways of K permeation in the cortical collecting duct (CCD) from K-restricted rabbits, we studied the effects of the following three maneuvers: 1) luminal amiloride addition; 2) luminal Ba addition; and 3) luminal Na removal. Luminal addition of amiloride (1 mM) significantly increased the 86Rb lumen-to-bath efflux coefficient (KRb), and this effect was fully blocked by the presence of 2 mM luminal Ba. Addition of 2 mM luminal Ba reduced KRb both in the absence of luminal Na and in the presence of luminal Na. In contrast to the effect of amiloride addition, removal of luminal Na significantly increased KRb, but neither 2 mM luminal Ba nor 4 mM luminal Ba totally abolished this effect. However, simultaneous addition of luminal Ba and Sch 28080 (10 microM) fully inhibited the increase in KRb upon luminal Na removal, indicating that luminal Na removal enhances Rb efflux in part via H-K-adenosinetriphosphatase (H-K-ATPase). To test whether Na acts as a partial agonist for cation efflux via the H-K-ATPase we examined the effect of Sch 28080 on the 22Na lumen-to-bath efflux coefficient (KNa). These studies were conducted in the presence of 0.1 mM luminal amiloride to block fully apical conductive Na efflux, and the effect of Sch 28080 on KNa was examined at two different ambient K concentrations. In the presence of 0.5 mM K, Sch 28080 (10 microM) significantly inhibited KNa from 47.6 +/- 4.8 to 35.0 +/- 6.8 nm/s (P < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanisms of rubidium permeation by rabbit cortical collecting duct during potassium restriction. 133 11

The rat MTAL secretes protons into the tubular fluid and thus absorbs bicarbonate at substantial rates. Yet the cellular mechanisms of H+/HCO3- transport in the rat MTAL remain largely unsettled. We have performed intracellular pH recovery studies with use of the fluorescent probe BCECF in suspensions of rat MTAL fragments. Luminal H+ secretion occurs by two mechanisms (each responsible for 50% of the normal pHi recovery rate): (1) an electroneutral Na+/H+ antiporter that has an Na-Km of about 11 mM and is inhibited by amiloride (Ki = 2.8 x 10(-5) M); (2) a primary H+ pump that is inhibited by 10(-4) M NEM and 10(-4) M omeprazole, but not by 10(-4) M vanadate or removal of external K. These results suggest the presence of a vacuolar H(+)-ATPase rather than a H(+)-K(+)-ATPase. Basolateral HCO3 exit occurs predominantly by a Cl(-)- and Na(+)-independent electroneutral K+/HCO3- symporter, that has an HCO3-Km of about 17 mM, and is partially inhibited by 10(-4) M DIDS. Basolateral HCO3- efflux was not accompanied by variations of membrane potential monitored with the Em-sensitive fluorescent probe DIS-C3-5, and was not affected by maneuvers that depolarize the cells. It was strongly inhibited by cellular K depletion and dependent on transmembrane K gradient. We conclude that the rat MTAL should secrete protons through both Na+/H+ antiporter and H(+)-ATPase, and that basolateral HCO3- exit should occur through an electroneutral K+/HCO3- symporter.
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PMID:Mechanisms of H+/HCO3- transport in the medullary thick ascending limb of rat kidney. 165 72

The insecticides mirex and chlordecone have previously been found to suppress the biliary excretion of a wide variety of compounds. In the present studies, the effects of mirex, chlordecone, and phenobarbital on the uptake of two endogenous organic anions, estradiol-17 beta(beta-D-glucuronide) (E217G), an estrogen metabolite, taurocholate (TC), a common bile acid, and an essential amino acid, L-alanine (L-Ala) (0.5 mM), into isolated rat hepatocytes was investigated. Female Sprague-Dawley rats were orally dosed with mirex (12.5, 25, and 50 mg/kg) or chlordecone (6.25, 12.5, and 18.75 mg/kg) dissolved in corn oil for 3 days and isolated rat hepatocytes were prepared 2 days later. Rats were also dosed orally with phenobarbital (50 mg/kg on the first day and 80 mg/kg for the next 4 days) dissolved in distilled deionized water, and isolated hepatocytes were prepared on the sixth day. Mirex significantly reduced the uptake of both organic anions (0.5, 10, and 50 microM E2 17G; 10 microM TC) into hepatocytes by 40-70%, whereas chlordecone had no effect on their uptake. Mirex at 50 mg/kg significantly reduced the Vmax for the low- and high-affinity E217G uptake sites by 70% and decreased the Km for the low affinity uptake site by 60%. Mirex also significantly decreased the Vmax for TC uptake from 1.11 to 0.82 nmol/min/mg protein but had no effect on its Km (23.2 vs 22.9 microM). Mirex at 50 mg/kg was also found to reduce the uptake of 0.5 mM L-Ala by nearly 40%. Phenobarbital had no effect on the uptake of E217G (0.5 microM), TC (10 microM), or L-Ala (0.5 mM). Mirex treatment had no effect on hepatic plasma membrane Na+,K(+)- or Mg2(+)-ATPase activity. Neither mirex nor chlordecone at 50-100 microM had any effect on the uptake of 10 microM TC when added directly to hepatocytes from naive rats. These results indicate that mirex decreases the transport of organic anions and L-Ala across the basolateral domain of the hepatocyte in addition to its inhibitory effects on biliary excretion.
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PMID:Mirex exposure inhibits the uptake of estradiol-17 beta(beta-D-glucuronide), taurocholate, and L-alanine into isolated rat hepatocytes. 169 54


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