Steroid metabolism in the corpus luteum of the ferret

Implantation in the ferret is believed to be induced by a luteal substance which acts in concert with progesterone (P4) and which is secreted sometime between Days 6 and 8 of pregnancy. This experiment was designed to identify the steroid products synthesized by ferret corpora lutea (CL) on these 2 days of pregnancy. CL were dissected from ferrets on Day 6 or 8 of pregnancy and incubated with [3H] pregnenolone (P3), [3H] P4, or [3H] dehydroepiandrosterone (DHEA). Controls with no tissue or with 50 microliters packed blood cells were incubated at the same time. After incubation of Day 6 CL with [3H] P3 for 180 min, 39% of the added label was found incorporated into P4, 3% into 17 alpha-hydroxyprogesterone (17 alpha-OHP4) and 1% into androstenedione (A). Incubation of Day 8 CL with the same precursor resulted in 35%, 1% and 0.65% of the label being incorporated into the previously mentioned products, respectively. Incubations of Days 6 and 8 ferret CL with [3H] P4 or [3H] DHEA confirmed these results, demonstrating activity of C21-steroid, 17 alpha-hydroxylase and delta 5-isomerase, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). These results suggest that ferret CL primarily accumulate steroids of the delta4 pathway on both Days 6 and 8 of pregnancy, with P4, 17 alpha-OHP4, A and testosterone (T) being the most abundant products after in vitro incubation. Thus, ferret CL appear to metabolize steroids in a manner similar to that observed in rats, sows and mares.