Effects of removal of calcium from bathing media on frog stomach

¹ Departments of Radiology and Engineering Physics, University of Louisville, Louisville, Kentucky, and Department of Physiology and Biophysics, University of Alabama Medical Center, Birmingham, Alabama

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.

Key Words: secretion and calcium • calcium lack on stomach • resistance of stomach and calcium • acid secretion and calcium • potential difference and calcium • gastric mucosa and calcium • anoxia on resistance of calcium-depleted stomach • DNP on calcium-depleted stomach • secretion, frog stomach • permeability, stomach to calcium

Submitted on December 14, 1964