Failure of the metopirone (Su4885) suppressed fetal adrenal glands to maintain corticosterone concentration of adrenalectomized pregnant rats.

Plasma corticosterone concentrations were measured following adrenalectomy of pregnant rats on the last day of gestation. Plasma corticosterone concentrations decreased 40 and 60 min after adrenalectomy by 36 and 32%, respectively, and regained the preoperative concentration 2 h following operation. When the fetuses were injected with an inhibitor of 11beta-steroid hydroxylase (Su4885) plasma corticosterone concentrations decreased 40, 60 and 120 min following adrenalectomy by 63, 67 and 71%, respectively. The results strongly suggest that the fetal adrenal glands are the source of plasma corticosterone in adrenalectomized pregnant rats.