Ontogeny of gastric mucosal permeability responses to luminal H+ and bile salt in the rat.

Gastric mucosal responses to intraluminal instillation of acid (10, 50, and 150 mM HCl) and acidified solutions of sodium taurocholate (10 mM) were measured in rats between 5 and 60 days after birth. Net loss of H+ and gain of Na+, K+, and protein into the gastric lumen remained low and stable up to 25 days after birth. After that there were dose-dependent increases in H+ loss and Na+ and K+ appearance in the gastric lumen. Luminal protein appearance did not change with any concentration of acid tested in any of the ages examined. Gastric instillation of sodium taurocholate resulted in an increase in the rate of H+ loss as well as Na+ and K+ appearance in neonatal rats after 12-14 days. Protein appeared in the recovered gastric instillate and increased in parallel with Na+ and K+. In response to bile salt treatment, ulcers were only evident after 35 days of age. Injection of 8-day-old rats with corticosterone acetate (250 mg/kg) did not affect the ionic fluxes or protein output in response to acid alone or acidified bile salt solutions. These studies indicate that intragastric acid loads did not increase the ionic permeability of the gastric mucosa until 25 days after birth. The permeability changes occur earlier (day 12-14) if sodium taurocholate is added to the acid instillate. Prior to that time the mucosal permeability characteristics of the neonatal rat stomach are not altered by instillation of either acid loads alone or bile salt solutions.(ABSTRACT TRUNCATED AT 250 WORDS)