The enterohepatic circulation of the metabolites of 17α-ethynyl[³H]estradiol in the rat

Abstract

1. The biliary metabolites of 17α-ethynyl[³H]estradiol (³H-EE₂) and their enterohepatic circulation were studied in female rats.

2. Rapid and extensive elimination of radioactivity in bile followed i.v. administration of ³H-EE₂. The metabolites consisted largely of β-glucuronides of 2-hydroxy-EE₂ and, to a lesser extent, 2-methoxy-EE₂.

3. Intraduodenally infused radiolabelled biliary metabolites underwent enterohepatic circulation; 15.6% (mean±S.D., n = 4) of the ³H was excreted in the bile of the recipient rats in 5.5 h. The metabolites excreted by the recipients were qualitatively and quantitatively similar to the infused metabolites.

4. The 1(4)-glutathione adduct of 2-hydroxy-EE₂ was synthesized, but was not observed in either the donors' or recipients' bile.