Potassium and the transmucosal resistance of the frog gastric mucosa

¹ Department of Medicine, University of California School of Medicine, San Francisco, California

The effects of modifications in the potassium concentration of nutrient solutions (K_n) on the transmucosal potential difference (p.d.), initial resistance (R_i), final resistance (R_f) and the calculated initial current flow (I_i) and final current flow (I_f) were studied in vitro with application of external currents by direct current analysis. Stepwise increase of K_n from 1 to 9 mEq/l. resulted in a 53% fall in p.d., a 14% fall in R_i and a 46% fall in I_i. The ratio of R_i:R_f remained constant at all K_n levels, i.e. I_f fell to the same extent as I_i. When K_n was raised to 40 mEq/l., the orientation of the p.d. reversed, indicating a net charge transfer of cation in excess of anion into the secretory phase. The ratio of the current flow at K_n > 1.0 mEq/l. to the current flow at K_n = 1.0 mEq/l. was found to vary linearly with K_n. These data suggest that elevation of K_n depresses active chloride transport while sustaining or enhancing the rate of hydrogen ion production. Alternative explanations of these results are discussed in the text.