Effect of the Bicarbonate Ion on Gastric Potential Difference

¹ From the Departments of Chemistry and Physiology, University of Louisville, Louisville, Kentucky

The effects on the gastric potential difference (P.D.) produced by the application of isotonic and diluted sodium bicarbonate solutions to the nonsecreting and secreting gastric mucosa of the dog are reported. These experiments were performed on anesthetized dogs using the chambered gastric segment preparation and were designed to test the hypothesis that the P.D. originates as the result of a bicarbonate ion gradient across the mucosa. Reversal of the bicarbonate gradient by replacing the 0.16 m NaCl mucosal fluid by 0.16 m NaHCO₃ did not result in a change in the P.D. in the nonsecreting or secreting stomach. With 0.16 m NaHCO₃ in contact with the mucosa there is a small net absorption of fluid. Considerations based on the laws of diffusion indicate that under these conditions the bicarbonate concentration in the pit and tubular lumina will reach appreciable magnitudes within a few minutes, and hence the origin of the P.D. cannot be ascribed to a bicarbonate ion gradient in the nonsecreting stomach.