Steroid metabolism by badger ( Taxidea taxus) ovarian tissue homogenates

Abstract

Tissue homogenates of badger ( Taxidea taxus) ovaries and corpora lutea have been incubated with 7α- 3H-pregnenolone together with either 4- 14C-androstenedione or 4- 14C-dehydroepiandrosterone substrates. Ovarian tissue from nonpregnant animals metabolized androstenedione very little, and 95% was recovered unchanged after a 3-hr incubation. Kinetic studies showed that pregnenolone was extensively metabolized via 17α-hydroxypregnenolone and dehydroepiandrosterone to androstenedione and possibly small amounts of testosterone. No detectable 3H-progesterone accumulated in these incubations. After removal of the corpora lutea, ovaries of two pregnant badgers in the pre- and postimplantation stages showed metabolic patterns of 7α- 3H-pregnenolone similar to that of ovarian tissue from the nonpregnant badgers. Luteal tissue from the postimplantation animal formed primarily progesterone, 17α-hydroxypregnenolone and androstenedione from 7α- 3H-pregnenolone, and testosterone from 14C-androstenedione substrate in 3-hr incubations. Similar tissue from an animal in the preimplantation stage of pregnancy formed less than half the amount of 3H-progesterone and eight times the amount of 17α-hydroxypregnenolone formed by the corpus luteum tissue from the postimplantation ovary. Dehydroepiandrosterone-4- 14C was 90% metabolized to androstenedione in the latter incubations. These results demonstrate the predominance of a Δ 5-pathway of pregnenolone metabolism to dehydroepiandrosterone and androstenedione in whole ovarian tissue homogenates from nonpregnant badgers and in ovarian tissue from pregnant badgers after the removal of the corpora lutea. The presence of 3β-ol-dehydrogenase, Δ 5-isomerase, 17α-hydroxylase, C 17–20-desmolase, and 17β-hydroxysteroid dehydrogenase enzymatic activities has also been demonstrated in badger corpus luteum tissue. No major qualitative differences were observed in the steroid metabolic patterns of similar tissue from badgers in different reproductive states.