Inhibition of Steroidogenesis in Neonatal Leydig Cells by Unknown Factor(s) Present in Spent Media of Androgen‐treated Cultured Testicular Cells from Adult Rats

Abstract

Treatment of cultured testicular cells from adult rats with 5α‐dihydrotestosterone (DHT; 10−6 M) or the synthetic androgen methyltrienolone (R1881; 10−6 M) inhibited Leydig cell 3β‐hydroxysteroid dehydrogenase/Δ5‐4 isomerase (3β‐HSD) enzyme activity, whereas no effect of both androgens on cultured cells derived from neonatal animals could be observed. The inhibitory effect of DHT or R1881 on Leydig cell 3β‐HSD enzyme activity, however, was abolished when adult cells were cultured in the presence of the antiandrogen cyproterone acetate (CPA; 10−6 M) or the protein synthesis inhibitor cycloheximide (CX; 1 μg/ml). Testicular cells from adult animals were also cultured in the presence of the different treatments described above, and the spent media was collected and thereafter used as conditioned culture medium (CCM) in subsequent experiments performed with neonatal cells. Dispersed testicular cells from neonatal rats were cultured for 12 days in McCoy's 5a medium or in CCM derived from R1881‐treated adult cells, and fresh culture medium or CCM was replaced every 2 days. The human chorionic gonadotropin (hCG)‐stimulated testosterone production of neonatal cells was abolished in the presence of CCM derived from R1881‐treated adult cells. Nevertheless, the steroidogenic response to hCG recovered when neonatal cells were cultured for two additional days in McCoy's 5a medium. Treatment of neonatal cells with increasing concentrations of hCG (0.1–10 ng/ml) resulted in a dose‐dependent augmentation in Leydig cell 3β‐HSD enzyme activity and testosterone production. A similar dose‐dependent activation of steroidogenesis was observed in gonadotropin‐stimulated neonatal cells cultured in the presence of R1881 or CCM derived from untreated cultures of adult cells. In the same experiments the gonadotropin‐stimulated steroidogenic activity of neonatal cells was almost completely abolished in the presence of CCM derived from adult cells challenged with R1881 for 2 days. In contrast, no inhibitory effect on hCG‐stimulated steroidogenesis was observed when neonatal cells were cultured with CCM from cells treated with R1881 in combination with CPA or CX. The mechanism(s) whereby CCM from androgen‐treated adult cells inhibited neonatal Leydig cell steroidogenesis was also investigated. The full replication of hCG‐stimulated steroidogenesis elicited by the membrane‐permeable cAMP analogue But2‐cAMP (0.5 mM), the non‐receptor activators of adenylate cyclase cholera‐toxin (CT; 1 μg/ml) and forskolin (FK; 50 μM), or the phosphodiesterase inhibitor 1‐methyl‐3‐isobutyl‐xanthine (MIX; 0.1 mM) was abolished when fetal—neonatal Leydig cells were cultured in the presence of CCM derived from R1881‐treated adult cells, suggesting that the inhibitory effect of CCM is exerted, at least in part, distal to the activation of the cAMP—protein kinase A pathway. These data show that CCM from androgen‐treated adult cells contains a newly synthesized factor(s) that has major inhibitory effects on neonatal cell steroidogenesis and suggest that one or more of the cellular mechanism(s) involved in the steroidogenic response to androgens differentiate spontaneously as puberty approaches.