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)

In an attempt to clarify the question of an involvement of the inhibition of intestinal glucose absorption in the mechanism of action of Metformin, we used several experimental approaches: 1 glucose/lactate measurement in rat portal blood in vivo and 2 in the venous effluent of an isolated perfused rat intestinal segment; 3 metabolism of freshly isolated enterocytes in vitro and tissue distribution of 3H-labeled Metformin was investigated both in vivo and in vitro. Metformin applied intraluminally had no significant effect on portal glycaemia after a glucose load, but lactate increased, whereas in vivo only a high Metformin dosage reduced portal glucose appearance significantly. Although high Metformin concentrations were found in gut biopsies, precise histological analysis in the isolated intestine revealed that it was absent from enterocytes; however the drug accumulated in villous lacteals. Intrarterially applied Metformin decreased glucose absorption in the isolated perfused ileo-jejunal segment. These data suggested that vascular Metformin boosted intestinal anaerobic glucose metabolism. Biochemical measurements performed on freshly isolated enterocytes showed that even high Metformin levels did not interfere with cell respiration or with Na+/K+ ATPase activity. Thus, our data agree with other recent reports, suggesting that even at nontherapeutic concentrations Metformin has no relevant inhibitory effect on intestinal glucose absorption. The data are discussed in the frame of previous divergent observations. The results suggest however that Metformin of vascular origin stimulates glucose consumption by the intestine, which then increases lactate output from the gut.
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PMID:Metabolic and drug distribution studies do not support direct inhibitory effects of metformin on intestinal glucose absorption. 771 76

In recent years, an electrogenic 2Na+/1H+ antiporter has been identified in a variety of invertebrate epithelial brush-border membranes of gut, kidney and gill tissues. The antiporter differs significantly in its physiological properties from the electroneutral 1Na+/1H+ antiporter proposed for vertebrate cells. In all invertebrate cells examined, the antiporter displayed a 2:1 transport stoichiometry, responded to an induced transmembrane potential and exhibited a high binding affinity for the divalent cation Ca2+, which acted as a competitive inhibitor of Na+ transport. A monoclonal antibody specific for the crustacean electrogenic antiporter inhibited 2Na+/1H+ exchange, but was without effect on Na(+)-dependent D-glucose transport. Immunoreactivity was localized at hepatopancreatic brush-border and vacuolar membranes, antennal gland coelomosac podocytes and posterior gill epithelial cells-all locations were published reports described unique cation exchange kinetics. Significant fractions of Ca2+ transport into invertebrate cells across brush-border membranes occurred by an electrogenic, amiloride-sensitive exchange process, probably by the 2Na+/1H+ antiporter, and this transport was markedly inhibited by exogenous zinc and cadmium. A recently identified electroneutral, amiloride-sensitive, hepatopancreatic epithelial basolateral Na+/H+ antiporter was uninfluenced by the brush-border monoclonal antibody, exhibited an apparent 1:1 transport stoichiometry and possessed a minimal divalent cation specificity. Calcium transport at this epithelial pole occurred by the combination of a Ca2+/Na+ antiporter, an ATP-dependent Ca(2+)-ATPase and a verapamil-sensitive calcium channel. These crustacean brush-border and basolateral transporters may play significant roles in calcification and heavy metal detoxification.
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PMID:Role of the invertebrate electrogenic 2Na+/1H+ antiporter in monovalent and divalent cation transport. 782 31

We have sequenced downstream of the last previously sequenced gene of the glucitol operon (gutABDMRQ) in E. coli and have found that gutQ is the last gene of this operon. Downstream of the gutQ gene is found a palindromic unit (PU or REP sequence), followed by a large open reading frame of 1515 (or possibly 1590) bps transcribed in the direction opposite to that of the gut operon. This open reading frame encodes a protein of 504 (or possibly 529) amino acids with a tripartite structure. The N-terminal "receiver" domain of 187 (or possibly 212) residues is homologous to the FhlA protein of E. coli, a transcriptional activator of formate hydrogen lyase. It may possess a short domain at its extreme N-terminus exhibiting sequence similarity to carbohydrate binding proteins. The central ATPase domain (236 residues) exhibits greatest sequence similarity to the HydG protein of E. coli, a transcriptional activator of labile hydrogenase. The C-terminal DNA binding domain (81 residues) is homologous to NtrX of Azorhizobium caulinodans, a protein involved in transcriptional regulation of nitrogen fixation. Sequence comparisons with well-characterized transcription factors suggest that ORF504 encodes a protein that hydrolyzes ATP to generate the open transcriptional initiation complex of sigma 54-dependent promoters, possibly in response to redox conditions and/or ligand binding. We propose that this tripartite transcription factor arose by fusion of gene fragments encoding its three constituent modules.
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PMID:DNA sequence of a gene in Escherichia coli encoding a putative tripartite transcription factor with receiver, ATPase and DNA binding domains. 789 55

Na+, K(+)-ATPase expression in the epithelia of rabbit gut-associated lymphoid tissue was measured using indirect immunofluorescence and confocal laser scanning microscopy. All four major sites of aggregated lymphoid tissue, i.e. Peyer's patch, sacculus rotundus, caecal patch and appendix, were studied. Na+, K(+)-ATPase expression was localized to the basolateral surface of cells of the follicle-associated epithelium (FAE) and adjacent villous or surface epithelia (non-FAE), where increased expression during enterocyte migration was evident. In the FAE, expression of Na+, K(+)-ATPase appeared to be lower in the specialized M cells than in enterocytic-type cells, although expression in both cell types was lower than in adjacent non-FAE. Quantification of immunofluorescent staining of Na+, K(+)-ATPase by confocal laser scanning imaging showed a reduction of expression in the FAE to approximately 20-60% relative to that in the adjacent non-FAE. These results are consistent with a primary role of the FAE in mucosal immunity with minimal involvement in active solute absorption.
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PMID:Heterogenous Na+, K(+)-ATPase expression in the epithelia of rabbit gut-associated lymphoid tissues. 807 55

Recently, a putative distal colon H(+)-K(+)-ATPase alpha-subunit has been identified and characterized (M. S. Crowson and G. E. Shull. J. Biol. Chem. 267:13740-13748, 1992). In the present study, we report the tissue and cell expression of this putative H(+)-K(+)-ATPase. The results indicate that, first, in the gut, the putative H(+)-K(+)-ATPase alpha-subunit is restricted to the distal part of the colon and is predominantly expressed in surface epithelial cells, in marked contrast to the alpha 1-subunit of Na(+)-K(+)-ATPase that is also expressed in glands. These data suggest that the H(+)-K(+)-ATPase alpha-subunit is a potential marker for terminal differentiation of distal colon. Second, in the uterus, the putative H(+)-K(+)-ATPase is restricted to the region of the myometrium between the inner and midmuscular zone that is very rich in vascular supply and nerve cells. This striking expression suggests that the H(+)-K(+)-ATPase may not be involved in the control of pH and potassium concentration of the uterine fluid but rather in distinct functions of vascular and/or nerve cells. Third, with the use of three independent and different approaches (Northern blot analysis, ribonuclease protection assay, and in situ hybridization), we were unable to detect any significant amount of H(+)-K(+)-ATPase transcripts in kidney tissue. Our data suggest that the putative distal colon H(+)-K(+)-ATPase is probably distinct from the kidney isoform. Finally, we report the sequence of a set of degenerate oligonucleotides that are useful to clone alpha-subunits of the Na(+)-K(+)-/H(+)-K(+)-ATPase gene family in different tissues and different species.
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PMID:A putative H(+)-K(+)-ATPase is selectively expressed in surface epithelial cells of rat distal colon. 823 99

1. The properties of Na+/K(+)-transporting ATPase in microsomal preparation from mid-gut of the grasshopper, Poekilocerus bufonius, were investigated and compared with the same enzyme from brain and excretory system. 2. Two components of ATPases activity are present in the three tissues studied. 3. The physiochemical properties of Na+/K(+)-transporting ATPase from mid-gut, brain and excretory system (hind-gut plus Malpighian tubules) are essentially the same. 4. The calculated values of PI50 were 2 (I50 = 1 x 10(-2) M), 3.7 (I50 = 2 x 10(-4) M) and 6.4 (I50 = 3.98 x 10(-7)) for Na+/K(+)-ATPase from mid-gut, excretory system and brain, respectively. The mid-gut contains the most ouabain-resistant Na+/K(+)-ATPase. 5. The results suggest that P. bufonius have developed some tolerance to toxic cardiac glycosides (CGS), but there is a possibility of autotoxicity as indicated by the presence of ouabain-sensitive ATPase from brain tissue. 6. It was concluded that the dissimilarities of Na+/K(+)-ATPases from different tissues of P. bufonius are probably due to tissue-dependent differences in ouabain sensitivity (or isoenzymes pattern) available in the same insect. 7. The atrophy of female flight muscle of P. bufonius suggests the possibility of physiological cost inflicted on insects consuming poisonous plants.
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PMID:Different ouabain sensitivities of Na+/K(+)-ATPase from Poekilocerus bufonius tissues and a possible physiological cost. 829 45

The large bowel daily absorbs passively 1500 ml of water down an osmotic gradient created by active electrolyte transports. The system is sustained by the enzyme Na(+)-K+ ATPase, the so called sodium-pump, present on the basolateral membrane of colonocytes. Some pathologic conditions may increase the amount of intraluminal water by inhibiting fluid absorbtion or enhancing fluid secretion. Diarrhoea represents the clinical counterpart of these alterations. Three forms of diarrhoea can be recognized on the basis of pathophysiological alterations. Diarrhoea is due to reduced ionic absorbtion, increased secretion or increased endoluminal osmolality. The drugs used to induce bowel actions or gut lavage increase also intraluminal water content by modifying transmural ionic transports. Laxatives or purges act by increasing either water secretion on endoluminal osmolality and therefore may produce systemic idro-electrolyte imbalance. To avoid this inconvenient an isosmotic electrolyte balanced polyethylene glicol solution (PEG-ELS) has been achieved. In addition orally administred PEG-ELS solution cleans the colon during its intestinal transit without producing relevant transmural water-ionic movements. Aim of this article was to describe the normal ionic transport, and its alterations in pathologic and pharmacologic conditions. Details on PEG-ELS were also given. This solution provides for an effective colon preparation for endoscopic or surgical procedures and resulted to be safe for patients with delicate fluid-electrolyte balance.
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PMID:[Ion transport in the colon]. 866 16

Oral cephalosporins are frequently prescribed beta-lactam antibiotics. Although it has been well established that cephalosporins compete with dipeptides for absorption in the intestine, using the same transport mechanism, little is known about the action of the drugs on the absorption of other nutrients. In this work the effect of cephradine and cefaclor on the absorption of D-galactose has been studied. Intestinal sugar uptake was measured in-vitro in pieces of intestine (50 mg) and brush-border membrane vesicles, and in-vivo in intestinal loops. Galactose uptake was inhibited by cephalosporins in a dose-related, time-dependent manner. In-vivo the inhibition appeared when the antibiotics were on the luminal side of the enterocyte and when they reached the gut from the basolateral side. Only the active transport of the sugar was modified; passive transfer did not change in the presence of cephalosporins. In brush-border membrane vesicles, cephradine and cefaclor did not alter sugar uptake in either sodium or potassium gradients. Both antibiotics non-competitively inhibited basolateral Na+,K(+)-ATPase activity. These findings show that cephradine and cefaclor inhibit the active-transport component of galactose absorption because they reduce the activity of the basolateral Na+,K(+)-ATPase.
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PMID:Interactions of cephradine and cefaclor with the intestinal absorption of D-galactose. 883 2

The isolation and study of Anopheles gambiae genes that are differentially expressed in development, notably in tissues associated with the maturation and transmission of the malaria parasite, is important for the elucidation of basic molecular mechanisms underlying vector-parasite interactions. We have used the differential display technique to screen for mRNAs specifically expressed in adult males, females, and midgut tissues of blood-fed and unfed females. We also screened for mRNAs specifically induced upon bacterial infection of larval stage mosquitoes. We have characterized 19 distinct cDNAs, most of which show developmentally regulated expression specificity during the mosquito life cycle. The most interesting are six new sequences that are midgut-specific in the adult, three of which are also modulated by blood-feeding. The gut-specific sequences encode a maltase, a V-ATPase subunit, a GTP binding protein, two different lectins, and a nontrypsin serine protease. The latter sequence is also induced in larvae subjected to bacterial challenge. With the exception of a mitochondrial DNA fragment, the other 18 sequences constitute expressed genomic sequence tags, 4 of which have been mapped cytogenetically.
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PMID:Identification and characterization of differentially expressed cDNAs of the vector mosquito, Anopheles gambiae. 891 45

Consumption of oil extracted from accidental or deliberate contamination of argemone seed to mustard seed is known to pose a clinical condition popularly referred to as Epidemic Dropsy. Several outbreaks of Epidemic Dropsy have occurred in the past in India as well as in Mauritius, Fiji Island, and South Africa. Clinico-epidemiological manifestations of argemone oil poisoning include vomiting, diarrhea, nausea, swelling of limbs, erythema, pitting edema, breathlessness, etc. In extreme cases, glaucoma and even death due to cardiac arrest have been encountered. The toxicity of argemone oil has been attributed to two of its physiologically active benzophenanthridine alkaloids, sanguinarine and dihydrosanguinarine. Histopathological studies suggest that liver, lungs, kidney, and heart are the target sites for argemone oil intoxication. Studies have shown to elucidate the cocarcinogenic potential of argemone oil that can be correlated with the binding of sanguinarine with a DNA template. Pharmacological response in intestine revealed immediate stimulation of tone and peristaltic movements of the gut in the sanguinarine-treated animals. Argemone oil/Sanguinarine caused a decrease in hepatic glycogen levels which may be due to the activation of glycogenolysis leading to an accumulation of pyruvate in the blood of Epidemic Dropsy cases. The increase in pyruvate levels causes uncoupling of oxidative phosphorylation leading to breathlessness, as observed in patients. Sanguinarine has been shown to inhibit Na+, K(+)-ATPase activity of different organs such as brain, heart, liver, intestine, and skeletal muscle, which may be due to the interaction with the glycoside receptor site on ATPase enzyme, thereby causing a decrease in the active transport of glucose. Argemone oil/alkaloid showed a Type II binding spectra with hepatic cytochrome P-450 (P-450) protein, thereby causing loss of P-450 content and an impairment of phase I and phase II enzymes. A green fluorescent metabolite of sanguinarine, benzacridine was detected in the milk of grazing animals. The delayed appearance of this metabolite in urine and feces of experimental animals suggests the slow elimination of the alkaloid. Argemone oil enhances hepatic microsomal and mitochondrial lipid peroxidation, indicating that these two organelles are the sites of membrane damage. Furthermore, studies suggest that singlet oxygen and hydroxyl radical are involved in argemone oil toxicity. Several bioantioxidants show protective effect in argemone oil-induced toxicity in experimental animals. The line of treatment in argemone-intoxicated epidemics has so far been only symptomatic, and specific therapeutic measures are still lacking, although it has been suggested that diuretics, bioantioxidants, steroids, vitamins, calcium- and protein-rich diet had some beneficial effects on Epidemic Dropsy cases.
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PMID:Clinicoepidemiological, toxicological, and safety evaluation studies on argemone oil. 918 56


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