Temporal effects of diethylstilbestrol administration in vivo on testosterone production in leydig cells

The temporal nature of estrogenic suppression of Leydig cell testosterone production was investigated. Adult rats were injected SC with 50 μg/100 g BW of DES or vehicle. Animals were sacrificed at 4, 8, or 12 h following a single injection or at 12 h following the latter of two daily injections for 1 or 2 days. Collagenase-dispersed interstitial cells were obtained, and population I and II Leydig cells were subsequently isolated on metrizamide gradients. Population I and II Leydig cells produced in vitro testosterone levels of 7.19 ± 0.86 and 12.84 ± 1.86 ng/10⁶ cells/3 h, respectively. These levels were increased to 10- to 13-fold in the presence of hCG of dbcAMP. No significant difference was noted in the responsiveness of these two populations to the in vitro additions. DES administration in vivo for 8-48 h resulted in dramatic and significant decreases in basal and stimulated testosterone production in vitro in both populations. However, DES treatment for 4 h was relatively ineffective in blocking testosterone production in vitro. The inhibitory patterns exhibited by the two populations differed considerably. Population I displayed a uniform degree of inhibition throughout the treatment, whereas population II exhibited a more transient suppression by estrogen. Thus, population II appeared to be less sensitive to the estrogenic effects than population I at 48, 24, and 12h of treatment. These data indicate that both population I and population II Leydig cells become sensitive to the inhibitory effects effects of estrogens between 4 and 8 h of in vivo treatment and suggest that certain differences exist between the two populations with respect to the temporal action of estrogens.