[The relationship between the level of hypophyseal adrenocorticotropic activity and the character of the tissue distribution of exogenously labeled ACTH].

Experiments were conducted on rats--intact, adrenalectomized and dexamethasone-treated; a study was made of the dynamics of incorporation into the kidneys, liver, adrenal glands, the thyroid gland and elmination from the blood plasma of iodated corticotropine of the hypophysis (Hum-ACTHid-28, Richter). It was revealed that the character of incorporation and elimination of the exogenous labeled ACTH depended on the state of the adrenocorticotropic activity of the hypophysis of the recipient rats. The period of semielimination of the iodated corticotropin of the hypophysis from the blood plasma of intact rats constituted 11.2 minutes. The hormone was not included into the parenchyma of the adrenal cortex. The rate of excretion through the kidney and catabolism in the liver of labeled ACTH increased with elevation of the level of endogenous ACTH in the blood. The period of semiexcretion of ACTH-I131 from the blood plasma of adrenalectomized animals constuted 6.4 min. With decrease of the level of endogenous ACTH in the blood due to the block of the hypophyseal secretion with decamethasone elimination of exogenous labeled hormone from the circulation was markedly retarded T1/2 = 17 min). Under these conditions ACTH-I131 was incorporated into the tissue of the adrenal cortex for 9 min. A conclusions was drawn that the period of semielimination of the exogenous iodated ACTH could be used as a criterion for the assessment of the adrenocorticotropic activity of the hypophysis of the animals-recipients.