Microelectrode studies of dog's gastric mucosa.

In anesthetized dogs, the potentials in the mucous coat and gastic cells were measured with microelectrodes. In the secreting stomach, with isotonic saline in contact with the mucosal surface, the orientation of the initial change in potential difference (PD) was often the same as that of the liquid junction potential between gastric juice and saline (the microelectrode became negative to a reference electrode in the saline) but the magnitude of the change was never more than 11 mv. On the basis of this finding an explanation is offered for the observation that in the secreting stomach replacing isotonic saline with isotonic HCl as the bathing fluid on the mucosal surface, results in a change in the serosal to mucosal PD of only 19 mv, which is 40% less than the liquid junction potential between gastric juice and saline. In the surface epithelial cells of both resting and secreting stomach, multiple levels of potentials were found. For the secreting stomach, the resistance between the interstitial fluid of the pit region and the fluid on the mucosal surface was 55 ohm cm(2), determined as the change in PD per unit of applied current across stomach. The implications of these findings are discussed with reference to the separate site theory of HCl formation.