Biliary excretion and enterohepatic circulation of estrone and estriol in rodents

Publisher Website
Google Scholar
Abstract
The biliary excretion and the enterohepatic circulation of labeled estrone and estriol were studied in rats, rabbits, and guinea pigs. The results were compared with data obtained in human subjects. The striking features of the studies in rodents were: the appearance of a preponderant amount of the radioactivity in bile within a relatively short period of time (4-6 hr.) after the administration of labeled estrone or estriol, and the low excretion in the urine of animals with biliary fistulas. The presence of significant amounts of radioactivity in the urine of intact animals indicates a substantial enterohepatic circulation. An outstanding feature was the diversity of results obtained in the various species studied and points towards a different metabolic handling of each steroid in each animal. In fact, there is considerable variation among the species with respect to the amount of radioactivity excreted via biliary and urinary routes. None of the animals handled estriol and estrone in a manner similar to that of human subjects. The role played by the nature of the conjugates excreted in the bile in affecting enterohepatic circulation and biliary excretion is discussed.