Comparison of the basolateral K+ conductance of the epithelial cells in frog gastric fundus mucosa.

Frog stomach transepithelial potential difference (Vt) and resistance (Rt) as well as the voltage divider ratio (VDR) and serosal membrane potential (VS) of surface epithelial (SEC) and oxyntic (OC) cells were recorded at rest and during stimulation with histamine. Serosal membrane K+ permeability was tested by sudden elevation of serosal K+ concentration from 4 to 13 mmol l-1. Stimulation decreased both Vt and Rt and increased VDR of the OC (from 9.4 +/- SD 3.0 to 14.4 +/- 4.1, n = 10, P less than 0.001), while VS remained virtually unchanged (-66.3 +/- 4.5 mV, n = 10); in SEC, however, VDR as well as VS increased, the latter from -67.3 +/- 5.9 to -75.7 +/- 7.3 mV, n = 9, P less than 0.001. Elevation of serosal K+ reversibly diminished Vt and Vs in both cell types. The transepithelial response to K+ increased after stimulation. However, the cell potential response delta Vs,K increased only in the SEC (from +16.0 +/- 2.9 to +18.5 +/- 2.6 mV, n = 9, P less than 0.001) but not significantly in the OC. We conclude that in frog stomach both OC and SEC are stimulated by histamine: the SEC respond with a hyperpolarization, which reflects an increase in their basolateral K+ conductance; the OC do not respond with a hyperpolarization, possibly because histamine increases the basolateral membrane K+ conductance as well as other ion conductances which have not yet been identified.