DISAPPEARANCE RATE OF ADRENOCORTICOTROPIC HORMONE FROM RAT’S PLASMA AFTER INTRAVENOUS INJECTION¹

Abstract

There is reason to suppose that the adrenocorticotropic hormone disappears rapidly from the blood stream but there are few or no determinations of the actual rate of disappearance. Male rats, of the Long-Evans strain, weighing 440 to 500 gms., were anesthetized with ether and injected intravenously, via the tail vein, with 5 m. of pure adrenocorticotropic hormone (ACTH). The hormone was prepared by the method of Li et al. (1943). After various time intervals, the animals were reanesthetized with ether and exsanguinated, blood being withdrawn from the inferior vena cava with heparin as an anti-coagulant. The plasma was separated by centrifugation and immediately assayed in doses of 0.5 cc. per 100 gm. body weight of assay animal, for the content of ACTH, by the adrenal ascorbic acid depletion method, as reported by Sayers et al. (1948). A standard curve obtained with this method using pure ACTH