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Stimulation of gastric acid and bicarbonate secretions by calcium in guinea pig stomach and amphibian isolated mucosa

1980; Wiley; Volume: 110; Issue: 4 Linguagem: Inglês

10.1111/j.1748-1716.1980.tb06689.x

1365-201X

Gunnar Flemström, Andrew P. Garner,

Ion channel regulation and function

Administration of Ca ++ (1.5 mg/kg i.v.) increased the output of both H + and HCO 3 ‐ from the stomach of the anesthetized guinea pig as determined by measurement of gastric intraluminal pH and pCO 2 . The rise in HCO 3 ‐ secretion was slightly greater than that in H + , resulting in a decrease in net acidity. Fundic mucosa isolated from frogs was used to study the mechanisms of the stimulatory actions. An increase in Ca ++ concentration in the nutrient (serosal) bathing solution from 1.8 to 7.2 mM stimulated H+ transport in this preparation. The effect of raising Ca ++ concentration was inhibited by the histamine H 2 receptor antagonist Metiamide and by increasing nutrient Mg ++ . Stimulation of H + transport, sensitive to Metiamide, was also observed with the calcium ionophore A23187 (4 μg/ml, nutrient side). The results indicate that at the mucosal level, Ca ++ stimulates H + transport by release of histamine from mucosal stores with properties similar to those of mast cells. Transport of HCO ‐ 3 in isolated mucosae was studied after inhibition of H + transport my metiamide. An increase in nutrient Ca ++ concentration stimulated the HCO ‐ 3 transport but the calcium ionophore had no effect. This action of Ca ++ was abolished by atropine (10 ‐ ‐ 6 M) and by raising nutrient Mg ++ , suggesting that it reflects release of acetylcholine from intramucosal nervous tissue. Thus Ca ++ stimulated gastric transport of both H + and HCO ‐ 3 in vivo and in vitro but evidence for a direct action on the transporting (parietal and epithelial) cells was not obtained.