Uptake and conversion of progesterone and testosterone to 5alpha-reduced products by enriched gonadotropic and chromophobic rat anterior pituitary cell fractions.

Monodispersed cells from anterior pituitaries of male rats were prepared by Pronasedissociation and incubated with [3H]progesterone or [3H]testosterone. The cells were then separated into enriched fractions consisting of gonadotropic, somatotropic or chromophobic cells by velocity sedimentation at unit gravity for 4 h. The uptake of [3H]progesterone and [3H]testosterone by the gonadotropic enriched cell fraction was 1.8 to 3.2 times greater than the somatotropic and chromophobic enriched cell fractions. The gonadotropic and chromophobic enriched cell fractions metabolized [3H]progesterone and [3H]testosterone appreciably. The principal metabolites were identified and quantitated by reverse isotopic dilution. After incubation with [3H]progesterone, the principal metabolite was [3H]5alpha-dihydroprogesterone which ranged from 11.5% for the gonadotropic cells to 7.6% for the chromophobic cells. Smaller amounts of 3alpha-hydroxy-5alpha-pregnan-20-one (3.7 to 4.8%) and 20alpha-dihydroprogesterone (2.1 to 4.3%) were also identified. After incubation with [3H]testosterone, the principal metabolite was 5alpha-dihydrotestosterone which ranged from 12.6% for the gonadotropic cells to 10.3% for the chromophobic cells. Smaller amounts of 5alpha-androstane-3alpha, 17beta-diol (4.1 to 5.5%) and androstenedione (1.8 to 3.0%) were identified. After incubation with [3H]progesterone or [3H]testosterone the same metabolites were also identified in the somatotropic cell fraction but were thought to be present because of contamination with gonadotropic cells. Dissociated pituitary cells from orchidectomized rats had a 2-fold increase in the uptake of [3H]testosterone and a greater metabolism of [3H]testosterone to 5alpha-dihydrotestosterone as compared to pituitary cells from intact rats (12.6 vs 25.7%).