Effect of 17alpha-ethinylestradiol on biliary excretion of bile acids

The effect of 17alpha-ethinylestradiol on biliary bile acids has been investigated. The ratio of cholate to chenodeoxycholate was diminished by the estrogen in cholestyramine-treated rats. With low doses, this effect was due to increased excretion of chenodeoxycholate. With the highest dose, the decreased ratio was due to a reduction in the levels of cholic acid. In the intermediate dosage range, both factors contributed to the decreased ratio. Prolonged treatment with 500 mug daily of 17alpha-ethinylestradiol produced a reduction in the excretory rate of both bile acids in animals treated or not treated with cholestyramine.