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)

This review has attempted to cover some of the findings that have been made in the mechanism of gastric secretion in recent years. It is hard to offer any firm conclusions, whether at the level of stimulus, metabolism, or the terminal process of secretion. However, some generalizations may be possible. At least amphibian gastric secretion is stimulated by cAMP as a second messenger, with histamine presumably acting as the primary messenger. The resultant metabolic change is due largely to a direct stimulation of catabolism, which in dog appears to be the metabolism of hexose, through the glycolytic process, the hexose monophosphate shunt, and the Krebs' cycle with cytoplasmic reduction and mitochondrial oxidation of pyridine nucleotides. No evidence could be obtained for changes in high energy phosphate or for lipolysis. One would expect gastric mucosal membranes during secretion to contain an anion-restricted electrogenic H+ pump, but they in fact contain an ATPase stimulated by monovalent cations and are insensitive to ouabain. In addition, hog or dog gastric membranes have the vectorial properties of H+ absorption, Rb+ extrusion, and ANS fluorescence enhancement with the addition of ATP, as well as protein phosphorylation by 32P dependent on a K+ gradient.
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PMID:Gastric secretion. 1 82

High concentrations of sulfolipids (four fractions having different hexose/sulfate ratio), intense enzyme activity (ATPase, oxoreductases) and evidence of mucines (staining with PAS and Alcian blue) in intercellular spaces were found in the lachrymal glands of Caretta caretta and Malaclemys terrapin adapted to sea water. In addition, the supranuclear region of the gland cells in Malaclemys terrapin is filled with mucin granules. These biochemical and histochemical observations indicate that these glands have a function in salt secretion in both species and are also consistent with a function of mucous secretion exclusively in Malaclemys terrapin. Limited signs of hypotrophy are not accompanied by changes in concentrations of sulfolipids in Malaclemys terrapin adapted to fresh water; only the reactions for enzyme activities are less intense. The mucous secretion is not affected, whereas, in correlation with changes in salt secretion, the change in ATPase activity is mot conspicuous. The correlations between the different components of the gland and salt secretion are compared with salt glands of birds and elasmobranchs.
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PMID:The sulfatides and some histochemical correlations of the lachrymal glands involved in salt secretion in Chelonia. 13 Nov 77

1. Study has been made of the effects of a variety of metabolic inhibitors and divalent cations (Ni2+ and Mn2+), normally after 5 min exposure, on the biphasic uptake of inorganic phosphate (Pi) exhibited by phosphate-deprived cells of Escherichia coli, strains AB3311 (Reeves met-) and CBT302 (a (Ca2+ + Mg2+)-ATPase-deficient mutant). 2. In AB3311 cells cyanide (1-10 mM) produced comparable reductions in phosphate uptake to anaerobiosis, but in both instances significant uptake was maintained. Examination of intracellular Pi concentrations showed that, despite these inhibitions, Pi is still concentrated 130 times compared to 394 times under aerobic conditions. Arsenate (100 muM) and iodoacetate (100 muM pre-exposed 15 min) both abolished anaerobic-supported uptake. Under aerobic conditions the former eliminated primary uptake while the latter reduced both phases of uptake 60%. The uncouplers, dinitrophenol (100-1000 muM) and carbonyl cyanide m-chlorophenyl hydrazone (CCCP) (50muM) produced very significant, but not complete inhibitions of both phases of uptake. Inhibitions by iodoacetate and dinitrophenol were additive while dithiothreitol protected against the effects of 50-250 mum CCCP. N,N'-Dicyclo-hexylcarbodiimide (DCCD), the potent inhibitor of membrane-bound (Ca2+ + Mg2+)-ATPase, at 10(-3) M caused significant inhibitions of aerobic- (approx. 60%) and anaerobic- (approx. 80%) supported uptakes thus suggesting some obligatory requirement for this ATPase. 3. CBT302 cells, like AB3311, supported Pi transport both aerobically and anaerobically. CCCP (50muM) reduced the primary uptake similarly to AB3311 cells, but the secondary uptake was less affected. DCCD (10(-5)-10(-3) M), as expected, showed no effects in contrast to AB3311 cells. 4. In AB3311 cells Ni2+ (10 mM) caused significant but different reductions of secondary (70%) and primary (33%) phases of phosphate uptake. Mn2+ (10 mM) showed a greater differential effect with the primary uptake being minimally affected and the secondary uptake being abolished (97%). Partial relief of these inhibitions by Mg2+ (10 mM), suggested that these ions compete with Mg2+ transport. High voltage electrophoresis studies showed that Ni2+ cause intensification in the labelling from 32Pi (i.e. during Pi uptake) of hexose phosphates and a reduction in the labelling of complex molecules left at the origin. With Mn2+, labelling of fructose 1,6-diphosphate was reduced, the triose phosphate area was intensified and an unknown area (X) was intensely labelled. When Mn2+ was combined with anaerobiosis, phosphate uptake though diminished in rate exceeded after 16 min the plateau level of uptake under aerobic conditions with Mn2+ present.
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PMID:Studies on phosphate transport in Escherichia coli. II. Effects of metabolic inhibitors and divalent cations. 13 92

Exposing micro-dissected pancreatic islets of non-inbred ob/ob mice to 2-5 mM-alloxan for 10 min decreased the ability of the islets to accumulate Rb+. Rb+ accumulation in pieces of exocrine pancreas was unaffected by alloxan. When islets were treated with alloxan in the presence of 2-20 mM-D-glucose, the Rb+-accumulating ability was protected in a dose-dependent manner. The protective action of D-glucose was reproduced with 3-O-methyl-D-glucose but not with L-glucose or D-mannoheptulose; mannoheptulose prevented D-glucose from exerting its protective action. The inhibition of Rb+ accumulation was due to a decreased inward pumping, since alloxan did not affect Rb+ efflux from pre-loaded islets. The inhibitory effect of alloxan had a latency of about 1 min, as revealed by experiments with dispersed islet cells in suspension. Alloxan-treated islets showed only a marginal decrease in ATP and no change in glucose 6-phosphate concentration. Although alloxan slightly decreased the hydrolysis of ATP in a subcellular fraction enriched in plasma membranes, this effect could not be attributed to a ouabain-sensitive adenosine triphosphatase. The plasma membranes exhibited a K+-activated hydrolysis of p-nitrophenyl phosphate; this enzyme activity too was insensitive to alloxan. Glucose may protect the univalent-cation pump by preventing permeation of alloxan via a path coupled to the hexose-transport system. Inhibition of the pump may be fundamental to the induction of alloxan-diabetes.
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PMID:Alloxan cytotoxicity in vitro. Inhibition of rubidium ion pumping in pancreatic beta-cells. 19 15

The uptake of [14C]-histidine and [14C]-histamine and the conversion of [14C]-histidine to [14C]-histamine was measured in suspensions of guinea-pig bone marrow cells rich in basophils. When comparable amounts of labelled histidine or histamine were added to equal numbers of basophils, the uptake of histidine was approximately forty-five times greater than that of histamine. Purified eosinophils, neutrophils and mononuclear cells incorporated only a small proportion of [14C]-histidine when compared to the basophil; [14C]-histamine uptake by all these cell types was virtually negligible. Histidine uptake and the amount of histamine formed de novo was directly related to the number of basophils, the time of incubation and the substrate concentration. Histidine uptake was decreased by agents which inhibit glycolysis, oxidative phosphorylation, Na + - K + -dependent ATPase, protein synthesis and RNA synthesis. Inhibition was demonstrable in a dose-dependent fashion and at concentrations which had no apparent effect on cell viability. Inhibitors of DNA synthesis, and of microtubule function, had no influence on histidine uptake. Cytochalasin B, an inhibitor of microfilament function, also decreased histidine uptake but only at concentrations previously showen to affect hexose transport. None of the agents tested affected the uptake of [14C]-histamine or the amounts of new histamine formed from the histidine that had been incorporated. These studies suggest that histidine is preferentially incorporated into the basophil; that the uptake depends on the integrity of a number of metabolic pathways, but that once the histidine is taken up these requirements do not apply to the formation of new histamine. In contrast, histamine appeared to diffuse passively, and in relatively small amounts, into all the cell types tested.
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PMID:Metabolic studies on the uptake of [14C]-histidine and [14C]-histamine and histamine synthesis by guinea-pig basophils, in vitro. 43 43

In dog proximal tubules in suspension, the addition of glucose increased significantly the ouabain-sensitive fraction of respiration, a response suppressed by phlorizin. The addition of alpha-methyl-D-glucoside (alpha-MG) had a modest effect and 3-O-methyl-D-glucoside (3-O-MG) had no effect. The different stimulation of the Na+,K(+)-ATPase activity elicited for each hexose could be explained by a different increment of net transepithelial flux of sodium induced by the sodium: hexose cotransport. This flux is a direct function of the transport characteristics of both luminal and antiluminal membranes of proximal cells for these sugars: glucose is rapidly transported by both membranes (allowing a large transepithelial flux of glucose: sodium) while alpha-MG is poorly transported by the basolateral, and 3-O-MG by the luminal, membrane of the dog proximal tubule (allowing a small transepithelial flux of hexoses and sodium). However the overall tubular respiration of dog proximal tubules was not increased by glucose addition because the increment in the ouabain-sensitive fraction was accompanied by a reciprocal decrement in an ouabain-insensitive but oligomycin- or N',N' dicyclohexylcarbodiimide (DCCD)-sensitive (or in the bafilomycin-sensitive) component of respiration. This component reflects the activity of a large BBM-bound H(+)-ATPase found in this species. The intracellular pH of dog proximal tubules in suspension was measured using the proton-sensitive fluorescent probe 2',7'-bis-2-(carboxyethyl)-5, (and 6)-carboxyfluorescein. Glucose application significantly alkalinized the cells. In contrast, other substrates such as lactate or acetate simultaneously acidified the cells and increased the ouabain-insensitive phosphorylative respiration of dog tubules. These observations suggest that a modulation of the activities of both the sodium and most probably the proton pump is elicited by substrate availability in suspensions of proximal tubules.
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PMID:Substrate-induced modulation of ATP turnover in dog and rabbit proximal tubules. 132 87

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

We have analyzed the development of Na(+)-dependent hexose transport during differentiation and during polarization of LLC-PK1, an established cell line with characteristics of the proximal tubule. When cell-cell contact was disturbed by a low extracellular Ca2+ concentration or by a phorbol myristate acetate (PMA) treatment, the development of Na(+)-dependent hexose transport was completely inhibited. The effect of PMA on the development of hexose transport could be uncoupled from its effect on the tight junctions. The PMA concentration needed for the latter effect was approx. 10-fold higher than for the former. As the primary cause of the PMA effect, an influence on the cytoskeleton is suggested. In contrast to PMA, the concentration dependence of both phenomena on the extracellular Ca2+ concentration was almost the same. Moreover, the incorporation of hexose carriers in the plasma membrane could be induced by changing the extracellular CA2+ concentration from low to normal. We conclude that there is a relation between the formation of tight junctions and the development of the Na(+)-dependent hexose carrier, possibly because Ca(2+)-dependent cell adhesion molecules play a role in both phenomena. However, a direct relation between Ca(2+)-dependent elements of the tight junctions and the insertion of the hexose carrier can not be excluded. The Ca(2+)-dependent development seems to be a common characteristic of apical membrane proteins in contrast to the development of the basolateral membrane protein, (Na(+)+K+)-ATPase.
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PMID:Influence of PMA and a low extracellular Ca2+ concentration on the development of the Na(+)-dependent hexose carrier in LLC-PK1 cells. 167 54

Adult rats injected with streptozotocin during the neonatal period displayed in the fed state moderate hyperglycemia. However, the percentages of glycated hemoglobin in erythrocytes and glycated lactate dehydrogenase in liver and pancreatic islets, as well as the sorbitol and glycogen content of the islets, were not significantly increased. Likewise, in intact islets, the ouabain-sensitive inflow of 86Rb+, and the ratio between 3H2O production from D-[2-3H]glucose and D-[5-3H]glucose were not different in control and streptozotocin-injected rats. These findings suggest that the alteration in both the mitochondrial catabolism of D-glucose and secretory response to the hexose previously documented in the islets of the latter animals are not attributable to factors such as the excessive nonenzymatic glycation of cytosolic proteins, sorbitol or glycogen accumulation, or impaired Na+, K(+)-adenosine triphosphatase (ATPase) activity. Although a contributive role of glucotoxicity in the impaired function of beta cell in this model of non-insulin-dependent diabetes should not be ruled out, it is speculated that streptozotocin might also cause a long-term damage of key mitochondrial dehydrogenases in the pancreatic beta cells and, possibly, their precursor cells.
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PMID:Neonatal streptozotocin injection: a model of glucotoxicity? 183 15

The Na(+)-dependent hexose carrier, an endogenous apical marker, develops during differentiation of LLC-PK1, an established cell line with characteristics of the proximal tubule. This development was inhibited by the microtubule-disrupting drugs, colchicine and nocodazole, while it was insensitive to lumicolchicine. This strongly suggests that microtubules are involved in the plasma membrane expression of the Na(+)-dependent hexose carrier. We also analyzed the increase in activity of endogenous apical and basolateral membrane proteins during the polarization process. The development of three apical (Na(+)-dependent hexose carrier, gamma-glutamyltransferase and alkaline phosphatase) and one basolateral membrane protein (Na+/K(+)-ATPase) was studied during the reorganization of LLC-PK1 cells into a polarized epithelium. Colchicine inhibited the rapid, transient increase in the expression of the Na(+)-dependent hexose carrier during this polarization process. A similar result was observed for the development of the other apical proteins, while the development of Na+/K(+)-ATPase seemed to be largely insensitive to colchicine. Our results are in agreement with the model that the vesicles containing the apical membrane proteins use microtubules as tracks to reach the plasma membrane. The transport of vesicles containing basolateral membrane proteins clearly occurs by a different pathway which is independent on an intact microtubular network. Since the inhibition by the microtubule-disrupting drugs was complete, it can be concluded that after disruption of microtubules, the apical vesicles do not use the basolateral pathway by default.
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PMID:Development of the Na(+)-dependent hexose carrier in LLC-PK1 cells is dependent on microtubules. 197 53


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