Potassium and the transmucosal resistance of the frog gastric mucosa

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Abstract
The effects of modifications in the potassium concentration of nutrient solutions (Kn) on the transmucosal potential difference (p.d.), initial resistance (Ri), final resistance (Rf) and the calculated initial current flow (Ii) and final current flow (If) were studied in vitro with application of external currents by direct current analysis. Stepwise increase of Kn from 1 to 9 mEq/l. resulted in a 53% fall in p.d., a 14% fall in Ri and a 46% fall in Ii. The ratio of Ri:Rf remained constant at all Kn levels, i.e. If fell to the same extent as Ii. When Kn 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 Kn > 1.0 mEq/l. to the current flow at Kn = 1.0 mEq/l. was found to vary linearly with Kn. These data suggest that elevation of Kn depresses active chloride transport while sustaining or enhancing the rate of hydrogen ion production. Alternative explanations of these results are discussed in the text.