FETAL ADRENALS OF RAT - CORRELATIONS BETWEEN GROWTH, CYTOLOGY, AND HORMONAL ACTIVITY, WITH AND WITHOUT ACTH DEFICIENCY

Growth, ultrastructure, and corticosterone content were studied in the adrenals of rat fetuses in late pregnancy, between Days 19 and 21. In the fetuses of intact mothers, the hypophysial corticostimulating activity decreased between Days 19 and 21. Ablation of the fetal hypothalamus by total removal of the brain, leaving the hypophysis in situ (encephalectomy), induced atrophy of the adrenals, changes in adrenal ultrastructure, and decrease in the adrenal corticosterone content. Such modifications were also observed in response to the ablation of the pituitary gland by decapitation. The hypothalamus was involved in the control of ACTH release in late pregnancy. When mothers were adrenalectomized on Day 14, in the absence of hypothalamic tissue, the pituitary gland of the encephalectomized fetuses showed some corticostimulating activity; indeed, the adrenals of these fetuses were heavier on Day 21 than those of the decapitated fetuses but smaller than those of the littermate controls, and the adrenal corticosterone content was also greater than in the decapitated but less than in the controls. Encephalectomy induced modifications in adrenal cytology less marked than those induced by decapitation. These data suggest that the pituitary gland and the hypothalamo-hypophysial complex are the sites of the corticosteroid-induced inhibition of the corticostimulating activity of the fetal hypophysis. © 1978.