The role of bile acids in the effect of ethinylestradiol on the biliary excretion of exogenous organic anions.

Ethinylestradiol (EE) has a cholestatic effect and decreases the biliary excretion of xenobiotics. In the present experiments, pretreatment with EE did not influence the biliary excretion of bile acids. On the other hand, the effect of EE on the biliary excretion of exogenous organic anions and on bile production was not influenced by administration of taurocholic acid (TC) or by depletion of bile acids by cholestyramine (CHOL). However, phenobarbital (PB) administered simultaneously with EE prevented the depressive effects of EE on the biliary flow and biliary excretion rate of rose bengal (RB). These results indicate that bile acids do not play an important role in the effects of EE and that changes in the bile salt independent fraction might be responsible for the effects of EE pretreatment on the biliary excretion of exogenous organic anions.