Fetal rat adrenal steroidogenesis and steroid transfer to adrenalectomized mother

On the 22nd day of gestation in rats, fetuses of acutely adrenalectomized mothers were injected subcutaneously with 0.43 muCi 4-14C-progesterone in 0.05 ml saline. Ten and 20 min after injection to fetuses, samples were taken to determine the 14C-progesterone metabolites in the plasma and adrenal glands. After extraction of the samples taken, the metabolites were separated by two-dimensional thin-layer chromatography and identified by autoradiography. 11-deoxycorticosterone, 18-hydroxy-11-deoxycorticosterone, corticosterone and 11beta-hydroxyprogesterone were identified in the plasma of injected fetuses, and, in far smaller amounts, in the plasma of their mothers. The plasma of noninjected fetuses also contained very small amounts of these corticoids. The fetal adrenal glands contained far smaller amounts of radioactive steroids than the fetal plasma did. The results obtained show that steroids of fetal origin can cross the placenta in and out, constituting evidence that the fetal adrenal glands are the only source of the plasma corticoids of their adrenalectomized mothers.