Testicular Steroidogenesis in the Common Marmoset, Callithrix jacchus

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Abstract
Studies were undertaken to determine the primary pathway of testicular biosynthesis of androgens in Callithrix jacchus, the common marmoset. Testicular fragments (25 mg) were incubated at 37 C in Krebs-Ringer bicarbonate buffer, pH 7.4, with pregnenolone-7-3H (10 µCi; 20 Ci/mm) or with progesterone-7-3H (10 µCi; 24 Ci/mm). Duplicate fragments were incubated with each substrate for 30 min, or for one, three and five hours, for a total of 16 individual incubations. Metabolites were separated by paper and thin-layer chromatography and their identity was established by recrystallization to constant specific activities and 3H/1 4C ratios. Pregnenolone was metabolized primarily to progesterone, with some conversion to 17α-hydroxyprogesterone, 20α-dihydroprogesterone, androstenedione, and testosterone. Progesterone was converted to 17α-hydroxyprogesterone, with some conversion to 20α-dihydroprogesterone, androstenedione, and testosterone. A substantial amount of the progesterone substrate was not metabolized throughout the incubation period. These data suggest a predominant delta-4 pathway in the testis of Callithrix, with possible defective 17α-hydroxylase activity.