Effect of Adrenocorticotropin Hormone Injections on Glucocorticoid Receptors in Chicken Thymocytes

The concentration of corticosteroid receptors in chicken thymocytes was determined by Scatchard analysis at various times after adrenocorticotropin hormone (ACTH) injection. Plasma corticosteroid was measured concurrently. As expected, circulating corticosteroid was significantly elevated by one or two im injections of ACTH and at .5 or 2 hr after a single iv injection. Concomitantly, there was about a 50% decline in the cellular concentration of cytoplasmic receptor sites. Although there was significantly more circulating steroid after two im injections than after one, and more at 2 hr than at .5 hr after a single iv injection, there was no significant difference between the concentrations of the cytoplasmic receptor in either case. The concentration of nuclear receptors was not altered by the ACTH injections employed.