Further studies on sudden potential drop in gastric mucosa.

The sudden potential drop (SPD) with its associated resistance drop, previously noted during anoxia when serosal pH was slightly decreased, can also be produced by substrate deprivation and reversed by addition of substrate. During a critical portion of the response, alternate stable high and low potential difference states can be selected by current pulsing. High Ca2+ in the serosal solution prevents the SPD response, and any condition preventing an SPD response will reverse the post-SPD potential. Although pH 1 mucosal solutions do not damage the tissue, an SPD under these conditions results in permanent loss of secretory activity, apparently due to increased H+ permeability in the post-SPD state. Cl-, Rb+, and urea fluxes are unchanged by the SPD. Since gastric anoxia and mild serosal acidosis might be expected during strong sympathetic stimulation, it is notable that an SPD can be produced in vivo by anoxia or vasoconstrictive drugs under conditions apparently in agreement with the in vitro requirements. This might provide a model system for studies of stress ulcer production. An equivalent circuit model for the SPD is presented, which agrees satisfactorily with the observations.