Concentration and localization of calcium in frog gastric mucosa

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Abstract
Removal of Ca++ from the solutions bathing the frog gastric mucosa results in an initial increase in resistance (first phase) and a decrease in the H+ secretory rate of about 40%. These effects are followed by a pronounced decrease in resistance (second phase) and a decrease in the H+ rate to zero. Restoration of Ca++ to the nutrient solution reverses these effects. Chemical analysis of the frog gastric mucosa by atomic absorption spectrophotometry showed that at the peak of the first phase there was a 50% loss of tissue Ca++ and no significant further loss by the time the H+ rate reached zero. Localization of Ca++ in the mucosal cells using glyoxal-bis (2-hydroxyanil) (GBHA) was found feasible. There was a marked reduction of the number of red GBHA-stainable Ca++ granules in the tubular cells at the peak of the first phase. In the second phase, by the time the H+ rate reached zero the granules were absent from the tubular cells. Restorationof Ca++ to the nutrient solutionresulted in a distribution of red granules in the tubular cells corresponding to that of the controls. The evidence supports the conclusion that GNHA-stainable Ca++ can readily leave and enter the tubular cells.