Metabolism and excretion of oestradiol-17β and progesterone in the Sumatran rhinoceros (Dicerorhinus sumatrensis)

H-labelled oestradiol-17b and 14 C-progesterone were injected i.v. into an adult female . Sumatran rhinoceros Dicerorhinus sumatrensis and all urine and faeces collected over 4 days. Of the injected steroid, 68% of 3 H-oestradiol and 89% of 14 C-progesterone were recovered. Peak excretion in urine occurred on day 1 for both steroids, and for faeces on day 2 for 14 C-pro- gesterone, and between days 2 and 3 for 3 H-oestradiol. Oestradiol metabolites were predominantly .nearly 70% excreted into the urine, while progesterone metabolites were almost exclusively . . ) 99% excreted into the faeces. The majority ) 70% of urinary excreted oestrogens consisted . of water-soluble i.e., conjugated forms, with ) 90% of these being glucuronides. In contrast, ) 75% of faecal oestrogen and progesterone metabolites were excreted as ether-soluble i.e., . unconjugated forms. HPLC co-chromatography of oestrogens in hydrolysed urine indicated only one peak of radioactivity, co-eluting with authentic oestradiol-17 b, whereas two peaks of radioactivity were found after HPLC of faecal oestrogens, the major one co-eluting with oestrone and the less prominent one with oestradiol-17b. Progesterone was excreted as numerous metabo- lites into the faeces. The three most abundant of these were identified using HPLC and gas . chromatography mass spectrometry GCMS as 5b-pregnane-3a ,20a-diol, 5b-pregnane-3a-ol-20- one, and a second pregnanediol, the exact structure of which could not be deduced. Measurement of urinary oestradiol-17b and faecal immunoreactive pregnanediol and 5a-pregnane-3a-ol-20-one