Influence of Ethynodiol Diacetate on the Formation of A-Homo-3Oxa-5?-Pregnane-4,20-Dione in Female Rats.

OBJECTIVE: To give more insight in the progesterone metabolism in rat after the treatment with the progestin ethynodiol diacetate. METHODS: Urinary excretion of the metabolites of subcutaneously administred (4-14C)-progesterone was studied in female rats. After an acid hydrolysis and extraction of urine the metabolites were analysed by thin layer chromatography and by gas chromatography-mass spectrometry. RESULTS: The most of radioactivity was excreted during the first 24 h, and total of 8.36 % has been recovered within four days. The excreted metabolites in urine were found as glucuronides and free steroids (80.72 %), and 19.28 % were determined as sulphates. Among detected metabolites, 5alpha-pregnane-3,20-dione, 3alpha-hydroxy-5alpha-pregnan-20-one and A-homo-3-oxa-5alpha-pregnane-4,20-dione were determined in the urinary extracts. The last one has not yet been identified before in rat urine. CONCLUSIONS: Consecutive injections of progestin ethynodiol diacetate (6 mg/kg b.w. daily) to adult female rats during 10 days (short-term treatment), or during 70 days (long-term treatment), starting on the 21st day of life, caused significant differences in the amounts of excreted 3alpha-hydroxy-5alpha-pregnan-20-one and A-homo-3-oxa-5alpha-pregnane-4,20-dione. Significant increase in the weights of pituitary, liver and kidneys were noted in rats treated with ethynodiol diacetate. The short-term treatment caused an increase, while after the long-term treatment a decrease of the ovarian weight was observed.