Fate of prostaglandin E2 in suckling rats after intragastric administration

[3H]Prostaglandin E2 was administered intragastrically to suckling rats at 10 micrograms and 0.1 microgram doses. At the higher dose, 91% of the radioactive label was recoverable at zero time, decreasing to 29% at 5 h. At the lower dose, 40% of the dose was recoverable at zero time, decreasing to 8% at 5 h. With time, the radioactivity in the stomach showed a steady decrease whereas it increased in the tissues. At the 10 microgram dose of [3H]prostaglandin E2 the amount of radioactivity showed a steady increase in the small intestine lumen and small intestine wall. In liver and kidney the maximum amount of radioactive label was found at 1 h. After 1 h the radioactivity began to decline in the liver, while the kidney remained at the same level for the entire 5-h period. At the 0.1 microgram dose of [3H]prostaglandin E2 the radioactivity in the small intestine lumen reached a maximum 3 h after gavage and thereafter declined. The amount of label in the small intestine wall increased for the entire 5 h. In liver and kidney the radioactivity peaked at 1 h, remained at the same level until the 3rd h, then exhibited a decline. Quantitation of the unmetabolized prostaglandin E2 reaching the various organs studied was possible 30 and 60 min after administration of the 10 micrograms dose of prostaglandin E2. At 30 min 42.9% of radioactive label present in the liver could be shown to be authentic prostaglandin E2. This corresponded to 0.64% of the original dose. At 60 min only 22.8% of the radioactive label found in the liver could be shown to be authentic prostaglandin E2, which corresponded to 0.46% of the administered dose. Similar results were found in the small intestine lumen, the small intestine wall and in the kidney. At 3 and 5h, none of the radioactivity found in these organs could be identified as authentic prostaglandin E2.