Differentiation of the fetal adrenal cortex of rats--its experimental observation in vivo.

The development and tissue differentiation of the adrenal cortex of rats were studied by giving experimental treatments to the fetus in vivo. A low-ACTH-condition was given to the fetus by administrating Dexamethasone through its mother, or directly into the subcutaneous tissue of the fetus, or by decapitation, brain aspiration or hypophysectomy. When the fetus was given the low-ACTH-condition for the last 5 days or more, the hypoplastic adrenal cortex developed specifically. It had nearly normal zona glomerulosa (ZG), and poorly differentiated zona fasciculo-reticularis (ZF-R) without differentiated ZF-R. The observing day was settled at 21 1/2 days old. The shorter the period of low-ACTH-condition was, the more thickened the differentiated zone (ZF-R) grew. On the contrary, the poorly differentiated layer became thinner in proportion to the period of low-ACTH-condition. The poorly differentiated cortical cell had ACTH-reactivity. It seems that the development and tissue differentiation of the ZF-R depend on fetal own ACTH, and poorly differentiated cortical cells appear below the ZG, and differentiate by ACTH and were gradually pushed inside. The zona glomerulosa develops and differentiates without dependence of ACTH.