Indomethacin fails to induce ulceration in the gastrointestinal tract of newborn and suckling rats

Little is known about the role of oral prostaglandins and maintenance of intestinal epithelial cell membrane integrity in suckling animals. The presence of prostaglandins in milk suggests that they may have potential cytoprotective effects. Thus, experiments were performed to determine whether indomethacin causes inflammation in the gastrointestinal tract of suckling animals. Rats were treated with daily intraperitoneal injections of indomethacin (10 mg/kg) starting on the 1st day of life. Unlike adult animals which develop intestinal lesions within 72 h, these rats did not develop intestinal ulcerations until weaning started on days 15 to 16. Indomethacin-treated suckling animals prevented from weaning did not develop intestinal lesions until they had access to solid food on day 23. Indomethacin-treated rats had large reductions in jejunal prostaglandin E2 content. In addition, prostaglandin E2 was present in rat milk in relatively large concentration as determined by radioimmunoassay. These studies suggest that exogenous prostaglandins present in milk may protect the intestine of suckling rats from indomethacin-induced inflammation; however, once weaning commences, prostaglandin insufficiency may develop leading to intestinal lesions. We speculate that suckling rats treated with indomethacin did not develop ulcerative lesions, despite a marked reduction in intestinal prostaglandin content, possibly due to prostaglandins present in milk.