Cl- - and K+-related fluctuations of ionic current through oxyntic cells in frog gastric mucosa.

Transport and conductance pathways for Cl- and K+ were studied in frog gastric mucosa using noise analysis techniques. The current-noise power spectra exhibited both Cl- - and K+-dependent characteristics. In Cl- -containing solutions, reductions in Cl- transport were associated with reductions of the overall noise power. Such changes appeared to reflect the movement of Cl- through the apical (mucosal) membranes of oxyntic cells. In Cl- -free solutions a K+-dependent Lorentzian component was detected in the power spectrum when applying a mucosally or serosally directed transepithelial K+ concentration gradient. This component was enhanced by 1) stimulating the oxyntic cells with histamine and 2) appropriate voltage clamping. It was reduced by mucosal Ba2+ in resting tissues and enhanced by mucosal Ba2+ in stimulated tissues. The K+ noise measured in gastric mucosae in Cl- -free solutions appeared also to be generated at the apical membranes of oxyntic cells. This is in analogy to previous findings in other gastrointestinal epithelia with fluctuating apical K+ channels. In the gastric mucosa these channels may play a key role in the mechanism of electrogenic H+ secretion.