Effect of Adrenocorticotropic Hormone (ACTH) on Hypophysectomized Adrenal-demedullated Rats.

Abstract

To determine the possible role of the adrenal medulla in the response of the adrenal cortex to pituitary adrenocorticotrophic hormone (ACTH), a pure prepn. of ACTH was administered for 15 days, at a daily dose of 0.2 mg. (divided into 2 intraperit. injns.) to 6 hypophysectomized 41 day-old [male] rats with intact adrenals and 6 similar animals which had been subjected to adrenal-demedullation 16 days previously. Treatment was begun on the day of hypophysectomy. Normal and adrenal-demedullated rats (6 each) were sacrificed as controls at the beginning of treatment, and 6 hypophysectomized and 6 doubly operated rats at the end. There was no difference in cortical wt. response to ACTH conditioned by the presence or absence of medullary tissue; the dose used was adequate to maintain the adrenal wt. at the time of hypophysectomy in both types of exptl. animals. The thymus was weighed as a further measure of cortical response, and its reduction had been equally drastic in both types of animate receiving ACTH. Frozen sections of the adrenals, stained with Sudan orange, showed that morphologically, the regenerated cortical tissue in demedullated rats had been protected against the effects of hypophysectomy as completely as the cortex of intact adrenals. The stimulating action of ACTH on the adrenal cortex of hypophysectomized rats was thus the same in the absence of the medulla as in the intact adrenal.