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)

Isolated guinea pig distal colons secreted acid into the mucosal bathing solution at a rate of 1.0-1.5 mumol X cm-2 X h-1 when the preparations were mounted in Ussing chambers and bathed with HCO3(-)-CO2-free solution. The rates of the acidification and alkalinization of the solutions were measured by a pH stat system or calculated from changes in the pH of the solution. The acid secretion was localized in the middle and distal parts of the colon but absent in the proximal part of the colon and the cecum. The mucosal acidification was accompanied by serosal alkalinization, the rate of the latter being approximately 60% of the former. A carbonic anhydrase inhibitor, methazolamide (10(-4) M), reduced both the mucosal acidification and serosal alkalinization rates by a similar magnitude. The mucosal acidification was completely abolished by mucosal K+-free conditions but unaffected by mucosal Na+-free conditions. Ouabain added to the mucosal solution promptly inhibited the acid secretion. Dose dependency of the inhibition conformed to the Michaelis-Menten equation with a half-maximal effect at 4 X 10(-6) M. When the pH of the mucosal solution was reduced to 4.3, the rate of the mucosal acidification remained essentially the same as that at pH = 7.4. Vanadate (10(-4) M) added to both the mucosal and serosal solutions significantly reduced the mucosal acidification rate. These results suggest that CO2 derived from the epithelial metabolism is hydrated by carbonic anhydrase in the cell and released H+ enters the mucosal solution while HCO3- enters the serosal solution. H+ exit across the mucosal membrane may be mediated by H+-ATPase that is sensitive to ouabain.
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PMID:Acid secretion in isolated guinea pig colon. 365 23

The bidirectional tubular transport of pyrazinoate (PZA) was studied in the isolated perfused proximal S2 segment of rabbit kidney. PZA reabsorption was a mechanism of large capacity, temperature-dependent and requiring a normal Na+/K+-ATPase activity. PZA reabsorption was reversibly decreased when lactate was added to the perfusate, indicating that it might occur through the sodium-lactate cotransport. The addition of PAH to the bath had a slight stimulatory effect on PZA reabsorption, suggesting a component of anion exchange in the overall PZA reabsorption. However, SITS added to either the perfusate or the bathing medium induced a non-significant decrease in PZA reabsorption, confirming the minor part of an anion exchange mechanism in this reabsorptive process. PZA reabsorption was not affected by the establishment of a bath-to-lumen H+ gradient, and was only moderately decreased after carbonic anhydrase inhibition by ethoxyzolamide, in opposition to what is known for the reabsorbed anion salicylate. The secretory transport of PZA was saturable and also dependent on a normal Na+/K+-ATPase activity. It is concluded that PZA is bidirectionally transported by facilitated mechanisms in the rabbit proximal S2 segment, one major reabsorptive mechanism appearing to be a sodium-anion cotransport, which might be the sodium-lactate reabsorbing mechanism.
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PMID:Pyrazinoate transport in the isolated perfused rabbit proximal tubule. 379 19

Open-angle glaucoma is treated primarily with drugs, some of which have been used clinically for years. These drugs include: 1) cholinergic agonists that increase aqueous humor outflow, 2) adrenergic agonists and antagonist that affect both aqueous humor formation and outflow, and 3) carbonic anhydrase inhibitors that decrease aqueous humor formation. Several new classes of drugs are being tested for efficacy and mechanism of action. They include: 1) the D-isomer of timolol that reduces aqueous humor formation without producing adrenergic blockade, 2) dopaminergic agonists and antagonists, including bromocriptine and butyrophenones that reduce intraocular pressure, and 3) cannabinoids that reduce aqueous humor formation and increase outflow. In addition, several other types of drugs, such as prostaglandins, diuretics, Na+,K+-ATPase inhibitors, and adenyl cyclase stimulators are just now beginning to be studied.
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PMID:A synopsis of recent developments in antiglaucoma drugs. 391 48

Three different isoenzymes of human carbonic anhydrase are now well characterized. Carbonic anhydrase I and II have been known for several years and are located in high amounts in red blood cells as well as in many other tissues. Carbonic anhydrase III, a protein showing CO2 hydratase and p-nitrophenylphosphatase activity was isolated from skeletal muscle some years ago. Earlier observations based on enzyme activity and radioimmunoassay studies have suggested that this protein is present in greater quantities in red skeletal muscles than in white ones. We have purified CA III from human soleus muscle and using obtained monospecific polyclonal antibody localized this protein in the same muscle fibers which show acid resistant ATPase activity. Using this protein as a marker for type I muscle fibers, fiber classification into type I and II could now be done also from paraffin embedded sections.
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PMID:Purification and localization of human carbonic anhydrase. III. Typing of skeletal muscle fibers in paraffin embedded sections. 393 Apr 40

Analytical subcellular fractionation of tissue whole homogenates and microanalysis of organelle marker enzymes were used to study the activity and subcellular localization of enzymes implicated in HCO3 secretion in rat duodenal and gastric antral mucosae. The following organelles, characterized by their marker enzymes, were located in the density gradients: cytosol (lactate dehydrogenase), plasma membrane (5'-nucleotidase), peroxisomes (catalase), mitochondria (succinate dehydrogenase), endoplasmic reticulum (Tris-resistant alpha-glucosidase), lysosomes (N-beta-acetylglucosaminidase), and brush-border membrane (Zn2+-resistant alpha-glucosidase and alkaline phosphatase). Compared with gastric antrum, rat duodenal mucosa contained over twice the activity of HCO3-ATPase and of Na+-K+-ATPase but less than one-tenth the activity of carbonic anhydrase. Duodenal HCO3-ATPase activity was observed in both mitochondrial and brush-border membrane fractions, whereas antral HCO3-ATPase activity was confined to mitochondria. Na+-K+-ATPase activity was found largely in the basolateral membrane (duodenum) and plasma membrane (antrum). In both tissues carbonic anhydrase activity was localized to the cytosolic fraction. These observations offer further evidence that differing biochemical mechanisms underlie HCO3 secretion by gastric and duodenal epithelia.
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PMID:Activities and subcellular localizations of enzymes implicated in gastroduodenal bicarbonate secretion. 608 73

We examined the inhibitory activities of branched-chain fatty acids of iso-C12:0 to iso-C16:0 on gastric secretion in rats. Consequently, iso-C13:0 and iso-C15:0 were found to have strong inhibitory activities on gastric secretion in rats. In the case of intraduodenal administration, iso-C15:0 also showed a significant inhibition of gastric juice secretion. Therefore, the effects of iso-C13:0 and iso-C15:0 on ulceration in pylorus-ligated rats and aspirin-induced ulcer were examined. At the doses of 10 and 25 mg/kg, iso-C13:0 and iso-C15:0 significantly decreased the ulcer index in pylorus-ligated rats, and aspirin-induced ulcer was also significantly inhibited at the doses of 25 and 50 mg/kg. Finally, effect of iso-C15:0 on pepsin, Mg++-ATPase and carbonic anhydrase, which are considered to play an important role in the mechanism of gastric juice secretion, was examined in vitro, centering around iso-C15:0 which showed a marked effect in gastric juice secretion inhibitory and anti-ulcerogenic activities. Iso-C15:0 showed inhibitory activity on pepsin and Mg++-ATPase, but entirely no activity on inhibiting carbonic anhydrase.
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PMID:Effects of branched chain fatty acids of iso-C12:0 to iso-C16:0 on gastric secretion and experimental ulceration in rats. 612 Feb 23

The pancreas is a 'leaky' epithelium and secretes a juice in which sodium and potassium have concentrations similar to those of plasma. The characteristic features of the secretion are its isosmolality and its high bicarbonate concentration. It is the latter that has attracted considerable attention. Secretion in the isolated cat pancreas is directly proportional to the bicarbonate concentration in the nutrient fluid. The ability of the gland to secrete weak acids has led to the view that because of the very different chemical nature of the anions, it is most likely that it is a component common to all buffers, the proton, that is subject to active transport. This is supported by the decrease in pH and the increase in rho CO2 of the venous effluent when secretion occurs and the sensitivity of secretion to the pH of the nutritional extracellular fluid. It is proposed that the cellular mechanisms are as follows: CO2 diffuses into the cell and is hydrated to carbonic acid under the influence of carbonic anhydrase. The bicarbonate ion so formed diffused into the ductular lumen and the proton is transported backwards through the epithelium with a proton pump (Mg2+ -ATPase) provisionally located in the luminal membrane and a hydrogen-sodium exchange carrier located in the basolateral membrane. Energy for the latter process is derived from the sodium gradient between extracellular fluid and cell. This gradient is maintained by a (Na+ + K+)-ATPase also located in the basolateral membrane. Chloride appears to be transported partly through a chloride-bicarbonate exchange mechanism but largely passively together with a large sodium and potassium component through the paracellular pathway. Osmotic equilibrium is likely to occur in the small ductules.
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PMID:Ionic transport mechanisms underlying fluid secretion by the pancreas. 612 41

1. Plasma sodium and chloride levels were determined in goldfish, Carassius auratus L., following acclimation to 5, 15, 25 and 35 degrees C. Carbonic anhydrase and (Na+/K+)-stimulated ATPase activities of gill and kidney were also assayed at both acclimation temperature and 41 degrees C. 2. Consistent with earlier findings this eurythermal species exhibits more variation in plasma composition with temperature than do the more stenothermal salmonids. Seasonal changes were also observed. 3. Despite differences in detail the overall pattern of transport enzyme activity change with acclimation was comparable to that previously observed in trout. The goldfish is, however, notable for high levels of renal carbonic anhydrase activity, and presumably employs this system more than does the trout to drive urinary recovery of ions by H+:Na+ and HCO3-:Cl- exchanges.
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PMID:Branchial and renal (Na+/K+) ATPase and carbonic anhydrase activities in a eurythermal freshwater teleost, Carassius auratus L. 612 44

The effects of thyrotrophin, hypophysectomy, and chronic treatment with thyroxine and methimazole on radioiodide uptake (thyroid/plasma (T/P) 125I-ratio), protein and DNA contents and activities of Na+, K+-ATPase, HCO-3 ATPase, and carbonic anhydrase (CA) of rat thyroid gland were evaluated. Thyrotrophin given to intact rats slightly increased thyroid iodide uptake, did not affect protein or DNA content, and slightly inhibited CA activity (units/g cell water). Hypophysectomy markedly decreased T/P 125I-ratio, increased protein content, decreased activity of Na+, K+ -ATPase, and slightly increased HCO-3 -ATPase(nmol/mg DNA per min) and CA (units/g cell water) activities. Thyrotrophin given to hypophysectomized rats (as compared with untreated hypophysectomized control animals) markedly increased T/P 125I-ratio, slightly decreased protein content and decreased Na+, K+-ATPase and CA activities. Chronic treatment with methimazole increased T/P 125I-ratio, decreased protein content, markedly increased NA+, K+-ATPase and HCO-3-ATPase activities, and decreased CA activity. Chronic treatment with thyroxine, in contrast, decreased T/P 125I-ratio, decreased Na+, K+-ATPase activity, and increased CA activity. There was a significant inverse correlation between T/P 125I-ratio and CA activity in follicular cells for the various induced functional states of the thyroid.
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PMID:Correlation of iodide transport with Na + ,K+ ATPase, HCO3-ATPase and carbonic anhydrase activities in different functional states of the rat thyroid gland. 612 35

The effects of acute (200 mg/kg) and chronic (20 mg/kg per day for 7 days) administration of acetazolamide on iodide transport, electrolyte distribution, and on carbonic anhydrase (CA), Na+, K+-ATPase and HCO3- -ATPase activities were evaluated in mouse thyroid glands. The effects of withdrawal from chronic administration of acetazolamide were also assessed. A single injection of a large dose of acetazolamide increased iodide uptake and completely inhibited CA activity. Chronic administration of acetazolamide only slightly increased iodide uptake; CA inhibition was also less marked than after acute administration. After withdrawal of acetazolamide, iodide uptake decreased and CA activity recovered rapidly to the control levels. Chronic treatment with acetazolamide decreased the content of water and increased the contents of protein and DNA in thyroid tissues. Withdrawal of the drug resulted in an increase in Na+ and K+ contents and a decrease in water content of this gland. These data demonstrate that CA activity has an inverse relation to the iodide transport and a direct relation TO Cl- content in the thyroid. Chronic administration of acetazolamide also increased iodide uptake by the thyroid glands of hypophysectomized rats and of turtles.
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PMID:Effects of acetazolamide on iodide transport, electrolyte distribution and activities of carbonic anhydrase, Na+, K+-ATPase and HCO3- -ATPase in mouse, rat and turtle thyroid glands. 613 3


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