Topical 16,16-dimethyl-prostaglandin E2. Effects on gastric morphology, hydrogen ion loss, and bicarbonate secretion.

Using a canine chambered stomach preparation, the effects of topical 16,16-dimethylprostaglandin E2 (dmPGE2) on gastric mucosal morphology, H+ loss and HCO3-secretion were assessed. Compared to control studies in which acid alone (100 mM HCl) bathed the epithelium, dmPGE2 (1 or 4 micrograms/ml), when applied to gastric mucosa in acid medium, significantly (P less than 0.01) enhanced H+ loss from the bathing solution in a dose-related fashion. These effects, however, were independent of any injury to the epithelium as confirmed by both light and electron microscopy. In other studies in which dmPGE2 was applied to gastric mucosa in neutral solution (150 mM NaCl, pH 7.0) using identical doses, a dose-related increase (P less than 0.01) in HCO3-secretion was observed. When the net HCO3-output (microEq/15 min) for each dose of dmPGE2 employed was compared with the net H+ loss (microEq/15 min) for each dose of PG used, no differences were noted. The correlation between H+ loss and HCO3-secretion was highly significant (r = 0.87; P less than 0.01). We conclude that with the doses studied, dmPGE2 is not damaging to gastric mucosa and that the apparent increase in H+ loss elicited by dmPGE2 in acid medium is due to acid neutralization secondary to HCO3-secretion.