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)

We tested the hypothesis that the gastric H+/K+ adenosine triphosphatase inhibitor, omeprazole, because of its different mode of action and pronounced inhibitory effect on gastric acid secretion, may be more effective in peptic ulcer that is refractory to histamine H2 receptor antagonist treatment than continuing the same therapy. Altogether 107 patients (duodenal ulcer, n = 88; prepyloric ulcer, n = 14; gastric ulcer, n = 3; mixed sites, n = 2) with refractory peptic ulcer - that is ulcer unhealed after at least two months' treatment with cimetidine 0.8 g or 1 g daily or with ranitidine 0.3 g daily - were randomly allocated to receive either omeprazole 40 mg daily (n = 54) or to continue treatment with the same H2 receptor antagonist and at the same dose (n = 53) for up to eight weeks. The patients in the two treatment groups were well matched demographically. Healing by 'intent to treat' analysis was as follows: at four weeks, omeprazole 46 of 54 (85%), H2 receptor antagonist 18 of 53 (34%) (p less than 0.0001); and at eight weeks, 52 of 54 (96%) and 30 of 53 (57%) respectively (p less than 0.0001). One patient was lost to follow up but of the 22 patients whose ulcers were shown to be unhealed at endoscopy after receiving continued H2 receptor antagonist treatment, 21 healed in four to eight weeks when changed to omeprazole. Daytime epigastric pain cleared at four weeks in 43 of 47 (91%) patients on omeprazole and in 32 of 46 (70%) on H2 receptor antagonists (p=0.01) and relief of all dyspeptic symptoms occurred in 39 of 47 (83%) and 23 of 45 (51%) (p=0.0009) patients respectively. Adverse events occurred in 11 of 54 (20%) patients on omeprazole and in 12 of 35 (34%) on cimetidine but in none on ranitidine. The events were mild and none required treatment withdrawal. The commonest event in patients on omeprazole was loose stools or diarrhoea (n=5). Omeprazole was significantly better than continued H2 receptor antagonist treatment for the short term management of refractory peptic ulcer as judged by healing rate and pain relief, and it was safe.
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PMID:Treatment of refractory peptic ulcer with omeprazole or continued H2 receptor antagonists: a controlled clinical trial. 162 76

The H+/K(+)-ATPase is the dimeric enzyme responsible for H+ secretion by the gastric parietal cells. The present study examined the response of rat fundic mRNA levels of H+/K(+)-ATPase alpha-subunit and somatostatin to the inhibition of H+/K(+)-ATPase enzyme activity and gastric pH elevation by oral omeprazole administration. Omeprazole inhibits the alpha-subunit of H+/K(+)-ATPase covalently and stabilizes stimulated morphology of the parietal cell. After a single administration of omeprazole (100 mg/kg), H+/K(+)-ATPase alpha-subunit mRNA levels increased significantly by 57% at 3 h and remained elevated for 6 h, returning to the basal level by 24 h. After multiple administrations of omeprazole (100 mg/kg per day, every 24 h for 3 days), H+/K(+)-ATPase alpha-subunit mRNA levels were already elevated at the time of the last dose, reached maximum at 6 h (95% increase above control), and returned to the pre-treatment level after 36 h. Nuclear run-on assay indicated H+/K(+)-ATPase gene transcription was significantly increased by omeprazole pretreatment in vivo. In contrast, a significant decrease in fundic somatostatin mRNA occurred at 12 h after a single dose, and the inhibition was more pronounced and lasted longer after multiple doses of omeprazole. These data indicate that omeprazole, while effectively inhibiting H+/K(+)-ATPase activity, induces H+/K(+)-ATPase gene expression in the parietal cells. An inverse relationship exists between the regulation of somatostatin gene expression in fundic D-cells and H+/K(+)-ATPase gene expression. The increase in H+/K(+)-ATPase alpha-subunit mRNA could be due to alterations in extracellular gastrin/somatostatin ratios or could be induced by intracellular effects of omeprazole.
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PMID:Regulation of rat gastric H+/K(+)-ATPase alpha-subunit mRNA by omeprazole. 168 16

Interactions with the hepatic cytochrome P-450 microsomal enzyme system, as evidenced by statistically significant changes in pharmacokinetic parameters, have been described with some H2-receptor antagonists. Omeprazole is the first of a new class of antisecretory agents inhibiting gastric secretion by blocking hydrogen potassium ATPase. Omeprazole contains a benzimidazole moiety and thus has the potential to interact with the cytochrome P-450 enzyme group. In vitro, in vivo and human clinical studies have assessed whether such an interaction occurs, and the potential clinical consequences, in patients receiving omeprazole therapy. In vitro studies have demonstrated that omeprazole influences O-deethylation and N-demethylation in liver microsomes and the clearance and elimination half-life of antipyrine in isolated perfused liver preparations. Overall, the studies reviewed suggest that omeprazole has a differential affinity toward specific cytochrome P-450 isozymes. In vivo animal studies have demonstrated that omeprazole prolongs pentobarbital sleep times and half-life and decreases [14C]-aminopyrine elimination. Human clinical studies have not demonstrated the "all or none" effect of omeprazole on cytochrome P-450-mediated drug interactions, as is seen with cimetidine. These studies confirm in vitro findings that omeprazole is a differential inhibitor of drug metabolism: interactions have been demonstrated with the model drugs aminopyrine and antipyrine, and the therapeutic drugs diazepam, phenytoin, and warfarin but not with theophylline or propranolol. Although caution should be exercised when initiating omeprazole therapy in patients taking concomitant diazepam, warfarin, and phenytoin, clinically significant drug interactions appear unlikely.
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PMID:Clinical implications of drug interactions with the cytochrome P-450 enzyme system associated with omeprazole. 174 33

Omeprazole (CAS 73590-58-6), an H+, K+ ATPase inhibitor, is a potent suppressor of gastric acid secretion and a very active substance in the treatment of duodenal and gastric ulcers. The kinetic profile of omeprazole is well defined for healthy volunteers and for some high-risk population, but not so far for patients with liver disease. As the substance is mainly metabolized in the liver, changes in liver circulation and/or function might lead to changes in the pharmacokinetics of omeprazole. Aim of the study was to evaluate the kinetic profile in patients with liver disease and compare the results obtained in healthy volunteers, 16 subjects were included in the study: 8 patients with liver cirrhosis and 8 healthy volunteers. A single oral dose of omeprazole 20 mg was administered: plasma samples were collected for 24 h since omeprazole administration. The principal pharmacokinetic parameters were estimated for the two studied populations.
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PMID:Pharmacokinetics of omeprazole in cirrhotic patients. 185 16

Omeprazole is the first of a new class of gastric antisecretory drugs, proton pump inhibitors. It inhibits the H+,K(+)-adenosinetriphosphatase enzyme of the gastric parietal cell, resulting in potent, long-lasting suppression of basal and stimulated acid secretion. The drug is currently approved for treatment of gastroesophageal reflux disease and Zollinger-Ellison syndrome. In clinical trials, treatment with omeprazole results in rapid healing of duodenal ulcers; it is also effective in treating gastric ulcer disease. It is uniformly well tolerated without significant adverse effects, although animal studies linked profound long-term suppression of gastric acid secretion with the development of gastric carcinoids. Potential future uses include the prophylaxis of ulceration secondary to stress or use of nonsteroidal anti-inflammatory drugs, and the prophylaxis of recurrent peptic ulcer disease.
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PMID:Omeprazole: a new drug for the treatment of acid-peptic diseases. 193 56

Omeprazole, a benzimidazole compound which inhibits H+/K+ ATPase in the gut, is used in the treatment of gastroesophageal reflux disease. Clinical and experimental use of omeprazole has been associated with inhibition of the cytochrome P450-dependent metabolism of a few drugs both in vivo in man and in vitro in animals. In these experiments, in vivo administration of omeprazole to rats failed to inhibit the cytochrome P450-dependent metabolism of four prototypic drugs, testosterone or estradiol.
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PMID:Omeprazole and cytochrome P450-dependent hepatic metabolism: a comparison of endogenous and exogenous substrates in male rats. 194 96

Omeprazole, a substituted benzimidazole, is a specific inhibitor of the enzyme H+/K(+)-ATPase, which is found on the secretory surface of the parietal cell. This enzyme, the "proton pump," catalyzes the final step in acid secretion. Omeprazole is a powerful inhibitor of gastric acid secretion. At the time of writing, omeprazole has been licensed in the United States for the treatment of severe grades of gastroesophageal reflux disease (GERD) as well as GERD unresponsive to treatment with currently available agents, and for the treatment of Zollinger-Ellison syndrome and other gastric hypersecretory states. Most recently, it has been recommended by the FDA advisory committee for approval as first-line therapy in duodenal ulcer disease.
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PMID:Omeprazole. Overview and opinion. 200 54

Omeprazole is a specific inhibitor of H+,K(+)-ATPase or 'proton pump' in parietal cells. This enzyme is responsible for the final step in the process of acid secretion; omeprazole blocks acid secretion in response to all stimuli. Single doses produce dose-dependent inhibition with increasing effect over the first few days, reaching a maximum after about 5 days. Doses of omeprazole 20mg daily or greater are able to virtually abolish intragastric acidity in most individuals, although lower doses have a much more variable effect. Omeprazole causes a dose-dependent increase in gastrin levels. Omeprazole must be protected from intragastric acid when given orally, and is therefore administered as encapsulated enteric-coated granules. Absorption can be erratic but is generally rapid, and initially the drug is widely distributed. It is highly protein-bound and extensively metabolised. Its elimination half-life is about 1h but its pharmacological effect lasts much longer, since it is preferentially concentrated in parietal cells where it forms a covalent linkage with H+,K(+)-ATPase, which it irreversibly inhibits. Omeprazole binds to hepatic cytochrome P450 and inhibits oxidative metabolism of some drugs, the most important being phenytoin. Omeprazole has produced short term healing rates superior to the histamine H2-receptor antagonists in duodenal ulcer, gastric ulcer and reflux oesophagitis. It has also been shown to be highly effective in healing ulcers which have failed to respond to H2-receptor antagonists, and has been extremely valuable in treating patients with Zollinger-Ellison syndrome.
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PMID:Clinical pharmacology of omeprazole. 202 1

The H2-antagonist loxtidine and the H+/K(+)-ATPase inhibitor omeprazole inhibit gastric acid secretion and both have been associated with the appearance of gastric tumours in rat cancer studies. Loxtidine is not genotoxic in a range of in vitro and in vivo assays. As false negative results can occur if the organotropic nature of the drug is not considered, both drugs were evaluated using an assay which estimates the uptake of tritiated thymidine by cells of the gastric mucosa (the target tissue) in comparison with the positive control, N-methyl-N-nitro-nitrosoguanidine (MNNG), which others have shown to induce genetic damage in the stomach mucosa of rats. Such uptake may be, in part, indicative of unscheduled DNA synthesis (UDS) resultant from genotoxic damage. Serum gastrin levels were also determined at various times after either loxtidine or omeprazole treatment. Increased uptake of tritiated thymidine was only obtained after omeprazole or MNNG treatment, when this was estimated scintillometrically. The nature of the formulation of omeprazole was critical. The uptake of tritiated thymidine was greatest when omeprazole was administered in vehicle which had been buffered to pH 9. These effects were unlikely to be due to the trophic effects of gastrin since serum gastrin levels were similar after either loxtidine or omeprazole treatment. Autoradiographic analysis of stomach sections was also carried out and revealed a 2- to 3-fold increase in the number of labelled cells within the fundic mucosa as compared to the control values after treatment with MNNG or Losec (enteric coated granules of omeprazole).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Uptake of tritiated thymidine by cells of the rat gastric mucosa after exposure to loxtidine or omeprazole. 203 67

We have previously shown that an ouabain-sensitive H(+)-K+ exchange mechanism may be present in the apical membrane of guinea pig distal colon [Y. Suzuki and K. Kaneko. Am. J. Physiol. 256 (Gastrointest. Liver Physiol. 19): G979-G988, 1989]. The present study is aimed to demonstrate the presence of an ATPase responsible for this exchange. ATPase activity was determined in the crude membrane fraction of the colonic epithelial cell homogenate. ATPase activity under Na(+)-free conditions was increased by the addition of K+, with a half-maximal effect at 55 microM. This increase was completely abolished by 1 mM ouabain, suggesting the presence of an ouabain-sensitive K(+)-ATPase. The ouabain-sensitive K(+)-ATPase activity was inhibited by vanadate (100 microM) and N,N'-dicyclohexylcarbodiimide (100 microM) but was resistant to oligomycin (4.5 micrograms/ml) and NaN3 (1 mM). The ouabain-sensitive K(+)-ATPase activity was observed in the distal but not in the proximal colon, whereas Na(+)-K(+)-ATPase activity was distributed along the entire colon. Omeprazole (40 microM) reduced the colonic K(+)-ATPase activity by 31 +/- 6%, whereas it reduced the gastric K(+)-ATPase activity by 78 +/- 8%. These results suggest that the ouabain-sensitive K(+)-ATPase as demonstrated here is responsible for the colonic H(+)-K+ exchange. This ATPase could be similar to but is not identical with either Na(+)-K(+)-ATPase or gastric H(+)-K(+)-ATPase.
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PMID:Ouabain-sensitive K(+)-ATPase in epithelial cells from guinea pig distal colon. 213 61


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