Sex Differences in Fetal Sheep Adrenal Steroidogenesis

The formation of several steroids was determined in vitro in adrenals removed from 18 female and six male fetuses of 113–115 days' gestation and in two female and two male fetuses at near term (137–143 days). Samples were incubated with 14 C‐acetate and the formation of labeled steroids was determined by two‐dimensional paper chromatography. Protein and corticosterone concentrations were determined by chromophore absorption and acid hydrolysis fluorescence methods, respectively. Tissue corticosterone concentrations were significantly higher in female (0.145 ± 0.010 μg/mg protein) than in male (0.083 ± 0.010 μg/mg protein) adrenal tissue at both stages, whereas corticosterone formation was similar in both sexes. Cholesterol formation was significantly higher in female (0.103 ± 0.079 μM/mg protein) than in male (0.044 ± 0.011 μM/mg protein) adrenals at both stages. Both testosterone and estradiol were synthesized at higher rates in female than in male adrenals (52% and 33%, respectively), whereas pregnanediol formation was 21% higher in the male. These results indicate that significant sex differences exist in the formation of various adrenocortical hormones by fetal tissues. The relevance of these findings to better survival of female premature newborns from respiratory distress syndrome in contrast with male, is discussed.