The potential difference response of the human gastric mucosa to cimetidine

The effect of cimetidine on the dynamic transmucosal potential difference (PD) of the normal human gastric fundus was studied, to quantitate the influence of the hydrogen ion on measurements. PD was measured between an intravenous flowing bridge of isotonic NaCl and a perfused intragastric probe by means of two calomel half-cells. The probe was used for luminal infusion of different electrolyte solutions, which at the same time functioned as the mucosal measuring electrode. Cimetidine increased PD -12 mV during NaCl infusion. When gastric acidity was neutralized with isotonic NaHCO3, this change of PD decreased to -5 mV. We conclude that 60% of the PD increase seen after H2 blockade may be explained by the mere disappearance of H+ from the gastric juice, and the other 40% by changes in the gastric mucous membrane. PD decreased progressively as luminal NaCl content was lowered, but this reaction was reversed after cimetidine. These findings may be explained by a twofold decrease of transmucosal permeability to Na+ during H2 blockade.