Effects of calcium removal on bullfrog gastric mucosa

Abstract

Removal of calcium from isolated bullfrog gastric mucosae by serial washings in calcium-free solutions or by the addition of EDTA or citrate caused a fall in transmucosal potential difference, a rise in the mucosal conductance, and an apparent decrease in the rate of acid secretion as measured by the pH stat method. Unless the potential difference fell to values very nearly zero the short-circuit current was not significantly decreased. Unidirectional fluxes of chloride in both directions across the mucosa were increased by EDTA, but the net flux, or actively transported chloride, was not significantly altered. This suggests that the removal of calcium by these methods does not interfere with active chloride transport. The increased movement of sodium and sucrose across the mucosa after EDTA suggests that a large part of the permeability change is occurring at the spaces between cells. Because of the large permeability changes accompanying removal of calcium it is postulated that the process of H⁺ production is not directly inhibited.