Testicular testosterone content was measured between Days E15.5 and E21.5 (Fig. 1). It was 12.0 ± 2.0 pg/testis on E15.5 and increased on E16.5, E17.5, and E18.5 slightly to 32.2 ± 5.0, 45.6 ± 7.6, and 61.1 ± 6.9 pg/testis, respectively. A sharp and significant increase occurred between E18.5 and E19.5, to 126 ± 28.4 pg/testis (p < 0.05). Thereafter, there was a slight decline between E19.5-E20.5, and E20.5-E21.5 accompanied by a reciprocal increase in plasma LH. When the testicular testosterone data were reexpressed as concentrations in pg/mg of tissue, similar trends were observed (data not shown).
Stimulation of Fetal Testes by hCG and LH
The basal and hCG-stimulated rates of testosterone production were measured at 1, 2, 3, and 5 h of incubation of whole fetal testes and dispersed Leydig cells, and compared at different fetal ages (Figs. 3 and 4). The degree of stimulation in fetal testes and dispersed Leydig cells was much lower at early fetal ages (1.4-fold on El6.5) and increased dramatically at later ages (7.7-fold on E20.5). We found that the maximum steroidogenic capacity per unit weight of tissue was highest on El8.5 (data not shown). birth control pills
FIG. 3. The effect of hCG on testosterone production by incubated intact fetal testes on E16.5-E20.5. One testis from each fetus was incubated for 5 h in the absence (dotted bars) and the other in the presence of 1.0 jxg/L hCG (solid bars). Testosterone concentration in the medium was measured by RIA. Data points represent the mean ± SEM (n = 8-10 pairs of incubations). * Significant difference from the previous time point (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001).
FIG. 4. The effect of hCG on testosterone production by dispersed fetal rat Leydig cells on E16.5-E20.5. Fetal rat Leydig cells were dispersed as described in Materials and Methods, and incubated for 5 h in the absence (dotted bars) and the presence (solid bars) of 1.0 |j,g/L hCG. Testosterone concentrations in the media were measured by RIA. Data points represent the mean ± SEM (n = 6-8). * Significant difference from the previous time point (*p< 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001).