Effects of Antiserum to Adrenocorticotropin on Adrenal Growth and Function*

Abstract

The trophic action of ACTH was investigated in intact rats by selective neutralization of endogenous hormone with specific antibodies. Administration of antiserum to ACTH to male Sprague-Dawley rats ranging in age from 3-12 wk for a period of 6-10 days had no effect on adrenal weight but caused a highly significant decrease in serum corticosterone levels. The ability of adrenocortical cells isolated from antiserum-treated animals to produce corticosterone in response to exogenous ACTH was also significantly lower than that of adrenocortical cells derived from normal rabbit serum-treated animals. Administration of ACTH antiserum to unilaterally adrenalectomized animals did not prevent the increase in weight, cell number and DNA content of the remaining adrenal gland. The steroidogenic capacity of adrenocortical cells from antiserum-treated animals was significantly lower in comparison with the capacity of cells obtained from the adrenals of unilaterally adrenalectomized rats treated with normal rabbit serum or unoperated controls. Quantitative evaluation of the ultrastructural changes by morphometry showed that neutralization of endogenous ACTH with antiserum resulted in significant decreases in the absolute volumes of mitochondria, cytoplasmic matrix and nuclei, although the changes were not as large as after hypophysectomy. These results and earlier studies of the action of ACTH on the proliferation of adrenocortical cells in monolayer culture show that the trophic action of ACTH is concerned solely with the induction and maintenance of the steroidogenic capacity of the adrenocortical cells.