Development of gastric mucosal protection against acid in the rat. Role of corticosteroids and prostaglandins.

The ability of 16,16-dimethyl prostaglandin E2 (dmPGE2) to protect the gastric mucosa from acid-induced damage was assessed in suckling and adult rats. Suckling rats 9-11 days of age did not show protection with dmPGE2 at doses up to 100 micrograms/kg, whereas adult rats had an ED50 of approximately 2 micrograms/kg. The onset of responsiveness to dmPGE2 (5 micrograms/kg) occurred in the suckling rat at an age between 14 and 21 days. The "intrinsic" ability of the gastric mucosa to protect itself against acid-induced damage increased gradually between 7 and 21 days. The appearance of dmPGE2 sensitivity was unaffected by administration of hydrocortisone on day 7, although hydrocortisone alone induced a precocious development of the intrinsic protection against luminal acid. These data suggest that this mucosal protective property of the stomach appears during the end of the second week of life in the rat, just before the increase in acid secretory activity. This may be attributable to both the ontogenic appearance of a responsiveness to prostaglandins and an increase in circulating levels of adrenocorticosteroid hormones. Although the protective mechanisms responding to prostaglandins and the corticosteroids could be different, our results suggest that the two factors may act in concert to assure optimal protection against luminal acid.