ABSORPTION AND METABOLISM OF ESTROGENS FROM THE STOMACH AND DUODENUM OF PIGS

To determine the absorption and metabolism of 17 beta-estradiol (E(2)) by the stomach and liver of the pig, crystalline E(2) was placed in the stomach of prepubertal gilts. Blood samples were subsequently obtained from the hepatic portal and jugular veins and plasma was assayed for E(2), estrone (E(1)), 17 beta-estradiol-glucuronide (E(2)G), estrone-glucuronide (E(1)G) and estrone-sulfate (E(1)S). Concentrations of E(2), E(1), E(2)G and E(1)S rose in the hepatic portal vein within five min and remained elevated for several hr. Concentration of E(2) represented only 6% of the total estrogen detected in the hepatic portal vein during the sampling period, indicating that most of the E(2) was converted or conjugated prior to entering the hepatic portal vein. The metabolism of E(2) presumably occurred in the stomach mucosa because food had been withheld for 26 hr before infusion of E(2). Concentrations of E(2)G, E(1)G and E(1)S, but not E(2) and E(1), rose in the jugular vein and remained elevated for several hr. The lack of a rise in E(2) and E(1) in the jugular vein indicates that the E(2) and E(1) from the hepatic portal vein were completely converted and/or removed by the liver. Most of E(2) was converted to E(1) and then to E(1)G. The infusion of bile containing normal estrogens from pregnant gilts into the duodenum of prepubertal gilts resulted in a peak of E(1)G and E(2)G in the hepatic portal and jugular veins within a few minutes. This was followed in about 180 min by a second sustained rise. The first peak was essentially abolished by extracting E(1) and E(2) from the bile before infusion. The second peak failed to occur in gilts given antibiotics orally to reduce gut bacteria before infusion of bile.