TESTICULAR STEROIDOGENESIS IN THE CEBUS MONKEY THROUGHOUT POSTNATAL-DEVELOPMENT

There is scant information on testicular steroidogenesis during postnatal development in monkeys, particularly in New World species. Our purpose was to study the in vitro steroidogenic capacity of the Cebus monkey testis from birth to advanced puberty. Fresh testicular tissue was incubated in Medium 199 with or without hCG (10 IU/ml); and levels of pregnenolone (P-5), dehydroepiandrosterone (DHA), progesterone (P-4), androstenedione (A), testosterone (T), dihydrotestosterone (DHT), and 3 alpha-androstanediol (3 alpha-DIOL) were measured in tissue and incubation media by RIA. To determine the predominant steroidogenic pathway, the ratio between the concentrations of the 5-ene and the 4-ene T precursors was determined, and the relative conversion of H-3-P-5, and C-14-P-4 to T was calculated. The number of Leydig cells per testis was determined in all experimental groups. The testes of the Cebus monkeys could produce T in vitro without the addition of gonadotropins at all ages. T and the 5-ene precursors (P-5 and DHA) were the main steroids found within testicular tissue throughout postnatal development. T content per Leydig cell increased continuously with age, but testicular T concentration reached maximal levels at early puberty and did not change thereafter. The ratios between 5-ene and 4-ene T precursors ranged between 2.8 and 13.2, which suggested a predominance of the delta-5 pathway. This was confirmed by the finding that H-3-P-5 was more efficiently converted to T than was C-14-P-4. The T production relative to that of its 5-ene precursors progressively increased to reach maximal values in late puberty. The conversion of T to its 5 alpha-reduced metabolites (DHT and 3 alpha-DIOL) was low throughout maturation. Addition of hCG stimulated steroid production in vitro in infantile and late pubertal animals. After hCG stimulation, the delta-5 pathway remained predominant, the efficiency of T production in infantile monkeys increased to pubertal levels, and Sol-reductase activity decreased in infantile animals. We conclude that 1) the infantile testis produces T in basal conditions, and this capacity increases with age because of a parallel increment in the numbers and steroidogenic ability of Leydig cells; 2) acute responses to hCG are low in early puberty, in coincidence with the lowest numbers of mature Leydig cells in the testis; 3) the delta-5 pathway is predominant in the Cebus monkey testis; 4) the maximal efficiency of T production relative to its precursors is attained in late puberty; 5) the 5 alpha-reductase activity is low at all ages; and 6) the addition of hCG has a maturation-like effect on the steroidogenic function of the infantile testis.