Effect of Ethynyl Estradiol on Hepatic Excretory Function of the Rat

Abstract

Current knowledge concerning the effect of natural and synthetic estrogens on hepatic excretory function in man (1,2) and in animals (3) is based for the most part on changes in the rate of disappearance from plasma of compounds that are excreted in high concentration in bile. The increased retention in plasma of phenoltetrabromphthalein disulfonate (BSP) and phenoldibromphthalein disulfonate (diBSP) (1–3) has been attributed to a decrease in the transport maximum (Tm) of these compounds from the liver cell into the biliary canaliculus. Since Tm was considered to be independent of bile flow, it has been inferred that the hormone interferes with the active transfer process. However, it has been shown by O’Maille, Richards and Short (4) and others (5,6) that the maximum excretion rate of BSP is enhanced more than two-fold by an increase in bile flow rate. Therefore, changes in the hepatic excretion rate of compounds that are present in bile in high concentrations can be attributed to alterations in both bile flow and active transfer. To distinguish between these possibilities, the effect of ethynyl estradiol on bile flow and the concentration of sodium taurocholate and phenoldibromphthalein disulfonate was determined in bile fistula female rats.