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 mechanism of vitamin D-dependent intestinal calcium transport has been explored in experimental animals in vivo and in vitro with the aid of pharmacologic agents that inhibit steps in the translocation process. Glucocorticoids in vivo, but not in vitro, inhibit the mucosal-to-serosal flux (Jms) of calcium and thus reduce net calcium absorption. Chronic metabolic acidosis inhibits calcium transport in vivo through inhibition of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] production and by a direct effect in vitro on the enterocyte to decrease calcium Jms. Cellular functions that may be involved in the transport process have been inhibited in vitro, including brush border calcium uptake by calcium channel blockers; calmodulin-dependent Ca-activated ATPase by trifluoperazine; calcium binding to vitamin D-dependent calcium-binding protein (CaBP, calbindin) by theophylline and acidic lysosomal vesicle function by quinacrine, chloroquine and ammonium chloride. The results of these studies demonstrate the consequences of selectively inhibiting steps thought to be involved in calcium transport and suggest new directions for further research in elucidating mechanisms of cellular calcium transport.
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PMID:The use of pharmacologic agents to study mechanisms of intestinal calcium transport. 154 31

The common hookworm (Ancylostoma ceylanicum) infection of humans was studied in golden hamsters model system. Significant biochemical modulations were observed in hamster jejunal brush border membrane (BBM), the primary site of infection. Analysis of BBM at the peak of infection (3-weeks) revealed a marked decrease in the activities of sucrase, lactase and maltase, while activities of alkaline phosphatase, (Ca2+ + Mg2+)-ATPase and gamma-glutamyl transpeptidase were increased. Kinetic studies conducted with maltase, a superficially localised enzyme of jejunal BBM, revealed loss of enzyme active site during the infection. Among other constituents, the levels of cholesterol and triglycerides were significantly decreased with slight increase in phospholipid content in the infected animals. The hookworm infection also caused a decline in total hexose content indicating an altered membrane glycocalyx. Conversely, there was significant enhancement of hydroxyproline and sialic acid contents. SDS-PAGE analysis showed an enhancement in both low and high molecular weight proteins in jejunal BBM preparations of the infected group. Gel electrophoresis of glycoproteins further revealed the appearance of two additional peaks in the low molecular weight region and concomitant disappearance of a peak in the high molecular weight region. These results strongly support the view that the hookworm infection causes severe damage not to the site of attachment alone but also to the entire cell lining of the jejunum and therefore could influence overall digestion and absorption.
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PMID:Biochemical analysis of jejunal brush border membrane of golden hamster: pathogenic modulations due to ancylostomiasis. 159 19

Gentamicin and calcium compete for binding to various tissues including renal tubular brush border. Moreover, gentamicin has calcium channel blocking properties in cardiac and vascular tissue. Calcium channel blockade in vitro by nifedipine or verapamil decreases calcium uptake by renal tubular epithelial cells. To determine the acute in vivo effects of gentamicin on renal calcium handling, we administered gentamicin 10 mg/kg as an i.v. bolus to F344 rats. Within 30 min of administration fractional excretion of calcium increased from a mean of 11 +/- 2% (S.E.M.) to 128 +/- 37%. There was no change in glomerular filtration rate, or urinary sodium, potassium or phosphate excretion. Maximum calciuria occurred immediately after administration, was dose-related and was correlated to preadministration urinary calcium. Urine calcium concentration was also correlated to urinary gentamicin concentration. Urinary calcium returned to base-line values within 90 min of bolus gentamicin administration, but remained elevated if a gentamicin infusion was continued. Parathyroidectomy and dietary calcium content did not affect gentamicin calciuria. Tobramycin, a less nephrotoxic aminoglycoside in the F344 rat, had calciuric effects similar to gentamicin. Verapamil, a calcium channel blocker which is largely excluded from the urine, and potassium dichromate, a nonaminoglycoside proximal tubular nephrotoxin, had no effect on urinary calcium. The mechanism of aminoglycoside calciuria is unclear, but may be related to competition between aminoglycosides and calcium for brush border binding, intraluminal calcium channel blockade by aminoglycosides or aminoglycoside inhibition of basolateral calcium ATPase or Na-K ATPase.
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PMID:Aminoglycoside-mediated calciuresis. 162 95

The development of the Na/H antiporter was studied in renal brush border membrane vesicles (BBMV) from fetal and adult rabbits using isotopic and fluorescent techniques. The kinetics of the antiporter studied by 22Na+ uptake revealed that the Vmax was only 25% of that in the adult; however, the Km's for Na+ were not significantly different. These data were confirmed by a fluorescent assay using the pH-sensitive probe, acridine orange: the Vmax was significantly lower in the fetal BBMV. Conductive Na+ movement was estimated from amiloride-insensitive 22Na+ uptake and the rate of alkalinization induced by K+, an ion whose relative conductance was found to be similar to that of Na+. Although relative Na+ conductance was significantly greater in fetal BBMV, the lower Vmax in fetal vesicles could not be ascribed to this factor. Maternal administration of betamethasone (50 micrograms/kg intramuscularly) for 2 d before delivery significantly increased the Vmax of the antiporter to levels observed in the adult; Km was unaffected. Na/K ATPase activity increased fourfold after betamethasone, but the specific activities of four brush border marker enzymes and the kinetics of Na(+)-glucose cotransport were unchanged. These data indicate that there is a developmental increase in brush border Na/H exchange which is the result of an increase in the number and/or the turnover number of the carriers. Further, these data suggest that the postnatal increase in antiporter activity may be related to the surge in glucocorticoid concentration that occurs perinatally.
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PMID:Ontogeny of Na/H antiporter activity in rabbit renal brush border membrane vesicles. 164 51

The purpose of this study was to establish a method for preparing brush border membrane vesicles (BBMV) from bovine choroid plexus epithelium. Using the technique of divalent cation precipitation and differential centrifugation, we established and validated a procedure. The specific activity of Na+/K+ ATPase, a specific marker for choroid plexus brush border membranes, was enhanced greater than 14-fold in the final membrane preparation in comparison to its specific activity in the homogenate. The specific activities of marker enzymes for basolateral membranes, lysosomal membranes, and endoplasmic reticulum were enhanced less than fourfold in the final preparation. The presence of intact vesicles was ascertained by electron micrography and studies of osmotic sensitivity using isotopic uptake methods. Sodium-driven proline uptake was demonstrated confirming the presence of functional tightly sealed choroid plexus BBMV.
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PMID:Preparation of brush border membrane vesicles from bovine choroid plexus. 164 71

In kidney medulla, intercalated cells (ICs) all have an apical proton-pumping ATPase, but in the cortex, ICs with apical (type A cells) and basolateral (type B cells) proton pumps coexist. Proton pumps in proximal-tubule epithelial cells are located in a band of apical membrane at the base of the brush border. To determine the effect of microtubule disruption on proton-pump polarity in these cell types, we immunolocalized proton pumps in normal and colchicine-treated rat kidneys. In addition, NEM-sensitive ATPase was measured in brush-border (BBMV) and basolateral membrane vesicles from kidney cortex. Rats were injected with colchicine, and kidneys were fixed 4-24 h later. In both cortical and medullary IC, proton pumps were localized on vesicles that were scattered throughout the cell. A- and B-type ICs were no longer distinguishable on the basis of proton-pump polarity. In the medulla, no concentration of proton pumps at the basolateral pole of ICs was detectable. In proximal tubules, pumps were also scattered on vesicles throughout the cytoplasm. NEM-sensitive ATPase was reduced by over 60% in BBMV, and was also reduced in basolateral membranes, indicating no increased insertion of NEM-sensitive ATPase into basolateral membranes after colchicine treatment. We conclude that a change in the polymerization state of microtubules is not sufficient to account for the differential targetting of proton pumps in subpopulations of intercalated cells.
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PMID:Colchicine-induced redistribution of proton pumps in kidney epithelial cells. 165 75

Vanadate alters intestinal transport and may have a role in regulating cell function. To determine whether it influences calcium absorption, we tested the effects of acute and chronic vanadate administration on calcium absorption using single-pass perfusion of jejunal and ileal segments of the in vivo rat intestine. Acute vanadate administration increased the lumen-to-mucosa and net fluxes of calcium in both the jejunum and ileum. The increase was largely due to an enhancement of the saturable fluxes of calcium and was observed at 10(-4) M concentration of vanadate, but not at higher or lower concentrations of the oxyanion, except at the highest concentration used, 10(-2) M, where calcium absorption was inhibited. Chronic vanadate administration caused, on the other hand, no changes in calcium absorption. We have demonstrated previously that rat intestinal (Na+ + K+)-ATPase is inhibited by vanadate, an effect that could raise cell sodium and increase the efflux of sodium across the brush border membrane. The results suggest that the vanadate enhancement of calcium absorption may be related to an increased entry of calcium into the mucosa, possibly as a result of an augmented exchange through the Na+/Ca+ antiport system. Alternatively, vanadate may influence access to a calcium channel in the mucosal membrane of the intestinal epithelium, leading to the observed increase in absorption.
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PMID:Enhancement of rat intestinal calcium absorption by vanadate. 165 72

Decline in the specific activities of intestinal cytosolic glucose-6-phosphate dehydrogenase (G6PD) and isocitrate dehydrogenase (ICDH); brush border glucoamylase, and isomaltase; and basolateral (Na+, K+)-ATPase activities were observed during the establishment, acute phase and decline phase of infection in Giardia lamblia-infected mice. The degree of decline in the activities of various enzymes correlated well with the number of trophozoites counted in the jejunum. There appeared to be a gradual recovery of enzymatic activities during the decline phase of infection, when the number of trophozoites also declined. The decline in activities of these enzymes may contribute to malabsorption of nutrients during giardiasis.
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PMID:Alterations in enzymatic activities of the intestinal mucosa during the course of Giardia lamblia infection in mice. 1667 Jul 64

The plasma membrane of the kidney brush border is composed of two compositionally distinct microdomains, microvilli and clathrin-coated pits. To study their assembly we have immunolocalized brush border marker proteins in the developing proximal tubule epithelium of the neonatal rat and compared their time and site of appearance with those of basolateral markers, Na-K-ATPase and fodrin. The proteins studied were dipeptidyl peptidase IV (DPPIV) (microvilli), actin and villin (microvillar cytoskeletal proteins), glycoprotein 330 (gp330) (coated pits), and clathrin (coated pit cytoskeleton). Although apical microvilli and coated pits were first seen in the stage III nephron, many brush border markers including DPPIV, actin, and clathrin appeared earlier in the development and initially were not polarized. Only during stage III did they become concentrated at the apical membrane. Villin first appeared in the stage III proximal tubule where it was located diffusely in the cytoplasm and in lysosomes as well as along the apical membrane. It did not completely colocalize with actin until stage IV. Gp330 first appeared during stage III and from the beginning was restricted to the apical clathrin-coated membrane domains and endosomes. The results demonstrate that 1) the expression of renal brush border proteins during development is asynchronous, and 2) unlike the basolateral plasmalemmal domain, which is established early in nephrogenesis, brush border assembly occurs later, approximately coinciding with the onset of glomerular filtration.
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PMID:Assembly of distinctive coated pit and microvillar microdomains in the renal brush border. 173 97

Effects of the s.c. administration of various doses of estradiol propionate (E.P.; 25-500 micrograms/kg) on the activities of carbonic anhydrase (CA), Mg(2+)-dependent ATPase and Mg(2+)-dependent, HCO3(-)-stimulated ATPase (Mg(2+)-HCO3(-)-ATPase) in rat duodenal mucosa and kidney cortex, and on body weight, organ weight and serum concentrations of testosterone and estradiol-17 beta, were examined in adult male, female, testectomized and ovariectomized rats. In normal male rats, activities of cytosol CA and brush border Mg(2+)-HCO3(-)-ATPase in the kidney were increased in a dose-dependent manner and reached 1.6- and 2-fold of controls, respectively, after consecutive administration (daily for 7 days) of 500 micrograms E.P. with no changes in either enzyme activities in duodenal mucosa. The positive correlations (P less than 0.01) were observed by linear regression analysis between serum concentration of estradiol-17 beta and kidney cytosol CA or kidney brush border Mg(2+)-HCO3(-)-ATPase activities. In normal female rats, activities of cytosol CA and brush border Mg(2+)-HCO3(-)-ATPase in the duodenal mucosa, and brush border Mg(2+)-HCO3(-)-ATPase activity in the kidney were increased by E.P. administration (100 and 500 micrograms/kg, daily for 7 days), however, kidney cytosol CA activity did not change by any dosage. Behavior of a part of both enzymes to E.P. in testectomized rats was altered almost in the same way to that observed in normal female rats and vice versa in ovariectomized rats. Body weight was decreased, in general, by consecutive administration of E.P. in a dose-dependent manner, and kidney weight was increased by E.P. in both male and female rats.
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PMID:Sexual difference and organ specificity of the effect of estradiol on carbonic anhydrase and Mg(2+)-HCO3(-)-ATPase activities isolated from duodenal mucosa and kidney cortex of male and female rats: preliminary study with crude enzyme samples. 183 40


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