Steroidogenesis in ovarian tissue of a viviparous teleost, the guppy Poecilia reticulata

Abstract

1. 1. Homogenates of ovaries of 3- and 12-month-old guppies were incubated with pregnenolone-7α-3H and progesterone-4-14C, and with androstenedione-1,2-3H, respectively. 2. 2. From the double-labeled experiment, 17α-hydroxypregnenolone, 17α-hydroxyprogesterone, dehydroepiandrosterone, androstenedione and testosterone were isolated and identified by paper- and thin-layer chromatography, derivative formation and by recrystallization to constant specific activity. 3. 3. In the ovary of the guppy the delta-5 pathway in steroidogenesis predominates, as may be concluded from the 3H/14C ratios of the identified metabolites. 4. 4. From the androstenedione-1,2-3H incubation, ovaries of 12-month-old guppies appeared to be able to synthesize steroids with functional groups in the 11-position (11-ketotestosterone and 11β-hydroxytestosterone). 5. 5. The androgen synthesis in ovaries of older guppies may be considered as a possible explanation of the sex conversion occasionally observed