Relationship between maternal milk PGE2 and gastric acid secretion in newborn rats

We previously demonstrated that in rats gastric acid secretion declines after birth and drops steeply on day 12 of life. In the present study, we investigated the part played in this decline by prostaglandin E2 (PGE2) from maternal milk. PGE2 content was first measured in the milk of untreated dams 0, 1, 5, 10, 12, 15, and 18 days after parturition. PGE2 levels were high during the first 5 days (123.5-200.5 pg/ml), declined significantly between days 10 and 15 (56.6-85.4 pg/ml; P less than 0.05), and dropped to 18.4 pg/ml on day 18. We also found that depleting milk of PGE2 prevented drop of acid secretion in 12-day-old suckling rats. Injecting lactating dams with indomethacin significantly reduced milk PGE2 content by 65% vs. milk of untreated dams. Surprisingly, administration of sesame oil, the indomethacin vehicle to the dams, increased milk PGE2 content by 182%. In the pups of the indomethacin-treated dams, acid secretion did not drop. On the contrary, in vivo basal and histamine-induced acid output rose markedly by 40 and 50%, respectively, and in vitro the net movements of 36Cl and 22Na measured in the isolated stomach indicated that active Cl- secretion had resumed. Mucosal PGE2 did not appear to be significantly involved in early development of acid secretion because administration of indomethacin to pups from untreated dams did not significantly modify the secretion measured on day 12. Data indicate that maternal milk depletion of PGE2 prevents the drop of gastric acid secretion previously observed in 12-day-old pups and suggest that in infant rats maternal PGE2 plays a physiological part in regulating acid secretion.