Structural Changes in the Fetal Gonads and Gonaducts During Maturation of an Enzyme, Steroid 3β-ol-Dehydrogenase, in the Gonads, Adrenal Cortex and Placenta of Fetal Rats¹

Correlative studies were made on the structural differentiation of the genital system on fetuses from timed, pregnant Sprague-Dawley rats and the maturation of steroid 3β-oldehydrogenase, an enzyme system essential for the synthesis of most biologically active steroids except for estrogens. The enzyme was measurably present in the testis, adrenal cortex and placenta from 151/2 –20 1/2 days of gestation, and was not found in the ovary until 9 days following birth. The appearance of the enzyme in testicular Leydig cells antedates regression of the gonadal cortex in the testis and sexual differentiation of the gonaducts. (Endocrinology81: 565, 1967)