Mechanisms of protective activity of 16,16-dimethyl PGE2 and acetazolamide on gastric and duodenal lesions in rats.

16,16-Dimethyl PGE2 (16,16-dmPGE2), given orally at 10-30 micrograms/kg, had no effects on gastric acid secretion, or carbonic anhydrase activity, but did increase HCO3- secretion in both the stomach and duodenum of rats. 16,16-dmPGE2, at nonantisecretory doses, potently inhibited indomethacin- and water-immersion stress-induced gastric lesions and mepirizole-induced duodenal lesions in rats. Acetazolamide, given orally at 50 mg/kg, markedly inhibited carbonic anhydrase activity, but had no effects on gastric acid secretion and the basal and 16,16-dmPGE2-stimulated HCO3- secretion. Acetazolamide, at a nonantisecretory dose, had no effects on indomethacin-induced gastric lesions and mepirizole-induced duodenal lesions, but significantly inhibited water-immersion stress-induced gastric lesions. Combined administration of 16,16-dmPGE2 and acetazolamide did not influence the protective activity of 16,16-dmPGE2 on these lesions. The mechanism of the cytoprotective activity of 16,16-dmPGE2 may involve an increase in HCO3- secretion (nonmediated by carbonic anhydrase), while mechanisms involved in the effects of acetazolamide are apparently different.