Inhibitory effect of ouabain on in vitro and in vivo gastric acid secretion in the frog and the rat

Summary The in vitro and in vivo effects of ouabain on gastric acid secretion in the frog and the rat, the 2 species known to have different sensitivity to ouabain, were studied. It was found that ouabain was a potent inhibitor of histamine-stimulated acid secretion in the isolated frog gastric mucosa. Ouabain administered i.v. at dose levels far below the lethal range also produced a marked and significant reduction of histamine-stimulated gastric acid secretion in the anesthetized frogs and rats. It is considered that the inhibitory effect of ouabain on acid secretion could be partly related to ist specific antagonizing action on the Na⁺-K⁺-ATPase in the gastric mucosa.     

Stimulation of pyruvate carboxylation by gastric secretagogues

Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.     

Effect of bilateral adrenalectomy and parenteral betamethasone on gastric mucosal mast cell population in albino rats

Summary The histamine-laden mast cells gastric mucosa in albino rats are shown to degranulate on administration of Betamethasone, but they increase in number in adrenalectomized rats. It is concluded that Betamethasone, and also adrenal glucocorticoids incrase gastric secretion by liberating histamine from mast cells and histamine in turn acts on the gastric glands.     

Effect of bilateral adrenalectomy and parenteral betamethasone on gastric mucosal mast cell population in albino rats.

The histamine-laden mast cells of gastric mucosa in albino rats are shown to degranulate on administration of Betamethasone, but they increase in number in adrenalectomized rats. It is concluded that Betamethasone, and also adrenal glucocorticoids increase gastric secretion by liberating histamine from mast cells and histamine in turn acts on the gastric glands.     

Stimulation of pyruvate carboxylation by gastric secretagogues

Summary Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.This investigation was supported by Consejo de Desarrollo Científico y Humanístico de la Universidad del Zulia, and by CONICIT Grant S1-0455.     

Mg2+-HCO-3-ATPase and carbonic anhydrase in rat intestinal mucosa

Mg2+-dependent and HCO-3-stimulated ATPase activity was highest in the brush border (microvilli) of rat duodenal mucosa compared with that of the other gastrointestinal mucosa. This ATPase may be useful to neutralize the gastric acid in the duodenal lumen. Carbonic anhydrase seems to accomplish a subsidiary role in the above reaction.     

Stimulation of H+ ion secretion from the isolated mouse stomach by sodium fluoride

Summary The effect of sodium fluoride on H⁺ ion secretion was investigated in the isolated distended mouse stomach. It was found that sodium fluoride on its own caused dose-related stimulation of H⁺ ion secretion. Sodium fluoride did not inhibit H⁺ ion secretion induced by histamine. The possible mechanisms involved are discussed. It is considered that sodium fluoride might stimulate H⁺ ion secretion by causing histamine release and by increasing cyclic AMP formation in the intact gastric mucosa.     

Hydrochloric acid secretion of fetal rat gastric mucosa]

In Rat, spontaneous secretion of hydrochloric acid by gastric mucosa takes place before birth. From day 20 of gestation until birth, the pH of gastric content markedly decreases, reaching 3 pH-units in newborns. During this period, Cl- concentration in gastric juice increases, while p-CO2 remains constant.     

The action of ouabain in promoting the release of catecholamines.

It is suggested that ouabain promotes catecholamine release by causing a rise in intracellular Na+ which, in turn, causes an elevated steady-state level of intracellular Ca2+. It is suggested that the Na+-K+-ATPase is not directly involved in exocytosis at either adrenergic or cholinergic synapses.     

Gastric secretion during anaesthesia and its inhibition by metiamide and other drugs.

The histamine H2-receptor antagonist, metiamide, inhibits the acid gastric secretion produced by chloralose-urethane anaesthesia in dogs carrying gastric cannulae chronically. This secretion is also prevented by atropine and hexamethonium. "Spontaneous" gastric secretion of vagal origin in conscious dogs is also blocked by metiamide.     

Inhibition of diuresis in the tsetse fly (Glossina morsitans) by ouabain and acetazolamide.

Acetazolamide and ouabain, metabolic inhibitors which interfere with certain membrane transport systems, reduce the rate of water elimination by male Glossina morsitans morsitans. The results suggest that water is transported across membranes during diuresis and that a ouabain sensitive Na+K+ATPase and an acetazolamide-sensitive carbonic anhydrase are involved in diuresis.     

Isolation of a hexaprenylhydroquinone sulfate from the marine sponge Dysidea sp. as an H,K-ATPase inhibitor

A hexaprenylhydroquinone sulfate has been isolated as an H,K-ATPase inhibitor from a marine sponge Dysidea sp. It also inhibited phospholipase A2 as well as secretion of gastric acid in rats.     

The effect of a gastric mucus barrier on the dynamic response of a pH electrode

Hydrogen ion mobility in gastric mucus has been found to be reduced to a greater extent than that hitherto suspected, though at low pH (less than 4) and in buffer this mobility increases. Mucus, at an optimized pH, may therefore protect the gastric mucosa from acid digestion by providing a diffusion barrier.     

Immunological blocking of exogenous and endogenous secretin in the dog.

In mongrel dogs with chronic gastric and duodenal fistula the biological activity of secretin on exocrine pancreatic secretion could be blocked by preincubating the secretin injected with rabbit antisecretin antibody. In addition, the activity of endogenous secretin released by acid was markedly reduced by application of antibody. Since no such effect was observed after testmeal stimulation, secretin is most probably not released in a significant amount by the liquid meal used in this experiment.     

Pentagastrine,histamine et acide ascorbique de la muqueuse gastrique chez le rat

Summary Pentagastrin and histamine, 2 potent gastric acid stimulants, lower ascorbic acid in the rat's gastric mucosa. They give the same result as nerve stimulation by desoxyglucose. Explanation of ascorbic acid function in gastric physiology needs further work.     

Gastrin stimulated H+ secretion in amphibian gastric mucosa: Effect of tetrodotoxin

Summary The role of neural mechanisms in gastrin stimulated H⁺ secretion was studied using amphibian gastric fundic mucosa. Spontaneously secreting mucosae were converted to resting state (zero H⁺ secretory rate) using Burimamide. Following removal of burimamide, 3×10^–6 M tetrodotoxin did not block gastrin stimulation of H⁺ secretion indicating that neural mechanisms are not required.This work was supported by U.S. Public Health Service NIH Grant AM17315 and by the Medical Research Service of the Veterans Administration.     

Increase in Na+, K+ -ATPase enzyme units in liver and kidneys from essential fatty acid deficient rats.

(3H)-Ouabain binding to liver and kidney preparations was utilized to estimate the number of Na+, K+-ATPase enzyme units in livers and kidneys from rats fed 2% corn oil supplemented or fat-free diets. The specific (3H)-ouabain binding in liver and kidney preparations from fatty acid deficient rats was increased approximately 40%, but the affinity of the binding sites for ouabain (Kd-value) remained unchanged. The increased concentration of Na+, K+-ATPase enzyme units observed in the essential fatty acid deficient rats may contribute to the reduced body fat accumulation and elevated heat production observed in these animals.     

Modification of the action of pentagastrin on acid secretion by botulinum toxin.

I.v botulinum toxin after 60-90 min abolished the dose-response relationship between pentagastrin and gastric acid secretion in anesthetized rats and guinea-pigs. The toxin reduced but did not abolish the acid stimulatory effect of histamine. As expected, the acid response to vagal stimulation was abolished and that to methacholine in rats was unaltered by the toxin.     

A note on the mechanism of action of UV-irradiation of amphibian embryos

The actions on amphibian embryos of UV-irradiation, exposure to Li+ or exposure to ouabain show interesting parallels with their effects on spontaneous release at the presynaptic terminals of the neuromuscular junction. It is suggested that these treatments serve to raise intracellular Ca2+ ([Ca2+]i) in these examples, and that UV-promoted abnormalities in embryogenesis are a consequence of changes in [Ca2+]i at critical stages in development.     

Potentiation by taurine of the inotropic effect of ouabain and the content of intracellular Ca++ and taurine in the heart.

Under certain conditions, taurine (3.0mM) potentiated cardiac contractile response to ouabain in the normal medium. The potentiation by taurine was also observed in the low K+ medium, in which the positive inotropic effect of ouabain increased. The potentiation as seen in both media was, at least in part, due to the increase by taurine of Ca++ content in the heart. Taurine in the heart was not directly related to this potentiation.