Ca²⁺ Removal Effects on Bullfrog Gastric Mucosa in the Presence of Drugs

Abstract

Bullfrog gastric mucosa can secrete acid in vitro for more than 24 hr.In Ca²⁺-deficient media, the acid secretion measured by pH stat method gradually decreased to cease about 200min after the start of immersion in the media.When A23187 or quinidine, which are known to mobilize Ca²⁺ from the intracellular pools, was present on the submucosal side, a prolongation of the duration of acid secretion in the absence of Ca²⁺ was found.Dibutyl c-AMP also induced a similar prolongation.Histamine or theophylline not only prolonged the duration of acid secretion but also transiently increased the acid secretory rate over the control level.Based upon the known fact that there are different intracellular Ca²⁺ compartments, i.e. one related to the process of acid secretion and the other to the maintenance of junctional complexes, the present results of drug effects were discussed especially in regard to their Ca²⁺ mobilizing effects.Cessation of acid secretion in a K⁺-and Ca²⁺-deficient solution occurred much more quickly than that in a Ca²⁺-deficient or a K⁺-deficient medium.