Relationship Between the Pituitary Gland and the Corticosteroid-Binding Globulin in the Rat

Abstract

Changes in corticosteroid-binding globulin (CBG) activity of rat serum were measured by multiple equilibrium dialysis at 37 C. Adrenalectomy in male and female rats increased, and in adrenalectomized animals the administration of corticosterone or cortisol decreased CBG activity; cortisol was 5 times more portent than corticosterone. The increase in CBG activity after adrenalectomy was not observed in animals which were both adrenalectomized and hypophysectomized. The injection of estradiol into intact male rats resulted in a 43% increase in CBG activity, over noninjected controls; similar injections into either hypophysectomized or hypophysectomized-adrenalectomized animals did not alter the binding activity. An increase in the ACTH level by either unilateral adrenalectomy or by injection of ACTH into hypophysectomized-adrenalectomized animals did not affect the CBG activity. The results suggest that the pituitary gland is necessary for the increase in CBG activity observed after adrenalectomy or after estrogen treatment; the data also indicate that ACTH is not the pituitary factor responsible for the increase.