Intact biliary excretion of gastrically administered prostaglandin F2 alpha in rats: developmental differences

Tritium-labeled prostaglandin F2 alpha was administered via orogastric tube to bile duct-cannulated suckling and weanling rats to determine if maturational differences were present in the biliary excretion of prostaglandin F2 alpha and metabolites. Animals were killed 2 h after radioactivity administration. Characterization of radioactivity present in bile revealed age-related differences in biliary prostaglandin F2 alpha excretion. Suckling rats had a greater proportion of radioactivity migrating in chromatographic regions of greater polarity than prostaglandin F2 alpha. Compared with the weanling, a significantly greater amount of radioactivity cochromatographed with intact, unmetabolized prostaglandin F2 alpha (33.08 +/- 1.99 vs. 21.38 +/- 1.46). These results indicate that orogastrically administered prostaglandin F2 alpha can be absorbed from the gastrointestinal tract, transported to the liver, and subsequently excreted into bile and detected in an unmetabolized form in suckling and weanling rats. The enterohepatic circulation of milk-derived prostaglandin present in bile may contribute to the overall content of intestinal prostaglandins.