The transepithelial potential difference (Vt) and resistance (Rt) and the basolateral cell membrane potential (Vs) of oxyntic cells (OC) and surface epithelial cells (SEC) were measured in isolated stomachs of Rana esculenta. At rest, Vs of OC and SEC was virtually identical [-66.3 +/- 4.5 (SD) (n = 10) and -67.3 +/- 5.9 mV (n = 9)] and both cells responded to increasing serosal K+ concentration from 4 to 13 mmol/l with virtually the same depolarization (delta Vs,K) of +16.2 +/- 2.0 and +16.0 +/- 2.9 mV, respectively, while Vt declined by approximately half as much. Histamine (0.1 mmol/l) reduced Vt and Rt and increased the voltage divider ratio in both cell types, indicating a fall in basolateral membrane resistance. In the OC, this increase was neither associated with a significant alteration of Vs nor with a change in delta Vs,K. In the SEC, however, histamine markedly increased Vs to -75.5 +/- 7.3 mV (n = 9) as well as delta Vs,K to +18.5 +/- 2.6 mV, which was paralleled by an increase in delta Vt,K from 9.8 +/- 3.9 to +12.8 +/- 4.2 mV. The data indicate that 1) both OC and SEC respond to histamine, 2) both OC and SEC contain a basolateral K+ conductance that increases under histamine (in OC probably, in parallel with other ion conductances), and 3) in Rana esculenta the SEC contribute substantially to Vt.