Effects of removal of calcium from bathing media on frog stomach

Abstract

Removal of Ca++ from the solutions bathing the frog gastric mucosa results in an initial increase in resistance (first phase) and a subsequent marked decrease in resistance (second phase). During the first phase the H+ secretory rate is decreased by 39% and the potential difference (PD) by 10%. During the second phase the measured H+ rate decreased to zero and the PD to near zero. Anoxia or DNP, which ordinarily produce a marked increase in resistance, failed to do so in the absence of Ca++. Comparable effects of Ca++ removal are found with Cl–-free bathing solutions. Replacement of Ca++ to the secretory solution on the nutrient side reversed these effects. Addition of Ca++ to the secretory solution readily reversed the second phase but only partly reversed the first phase. The inability of Ca++ on the secretory side in contrast to Ca++ on the nutrient side to reverse completely the first phase indicates that the secretory membrane may be much less permeable to Ca++ than the nutrient membrane.

Action of histamine and of some H2-antagonists on gastric secretion ‘in vitro’

“…However the role of calcium in isolated gastric secretion is far from being elucidated. Apparently a direct correlation between calcium and gastric secretion was found by some authors [29,30] whereas the opposite was true in other studies [31,32]. Our experiments did not throw light on this complex problem inasmuch as Ca++-free solution decreased gastric secretion and ionophore A 23187 increased it; on the other hand drugs interfering at different levels with calcium ions were virtually ineffective.…”

Amylase secretion by the perfused cat pancreas in relation to the secretion of calcium and other electrolytes and as influenced by the extrenal ionic environment*

“…A calcium requirement for gastric acid secretion has also been demonstrated (Forte & Nauss, 1963;Jacobson, Schwartz & Rehm, 1965). The cause of inhibition in these and other electrolyte transport processes is difficult to assess.…”

Electrophysiological Effects of Ca Ionophore A23187 on Frog Stomach

“…Firstly, the frog gastric mucosa like the frog cornea actively transports C1-. Secondly, it had previously been shown that Ca2+ appears to be essential for the normal functioning of the acid secretory mechanism (12,13). The results of the present investigation with Ca ionophore A23187 are described herein.…”