The biliary and urinary metabolites of [3H]17α-ethynylestradiol in women

Abstract

1. The metabolism of 17α-ethynyl[6,7-³H]estradiol (³H-EE2) (50 μg) given orally was studied in two groups of women: (a) six subjects from whom duodenal bile samples were obtained after 4h by endoscopic aspiration; (b) two subjects with bile-duct (T-tube) drainage.

2. The first group eliminated 16.6 ± 7.8% (mean ± S.D.) of the dose in urine over 72 h, the second group 28.6% and 27.5%. Biliary excretion by the latter was 41.9% and 28.3% of the dose, respectively, during the first 24 h after dosing.

3. The metabolites excreted in bile and urine were largely polar conjugates: 1–12% of the ³H was ether extractable. Approx. 70–90% of urinary and biliary ³H was extractable following β-glucuronidase-arylsulphohydrolase hydrolysis. Both β-glucuronidase and arylsulphates were excreted.

4. Unchanged ³H-EE₂ was the principal ³H-labelled component of the glucuronide and arylsulphate fractions of bile, and it was a major component of urinary fractions. 2-Hydroxy-EE₂ and 2-methoxy-EE₂ were identified as conjugated biliary metabolites.