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

Abstract

Male rats injd. intraven. with 5 mg. of pure ACTH were anesthetized and exanguinated at varying time intervals, and the ACTH content of the plasma detd. by the adrenal ascorbic acid depletion method of Sayers. Control plasma contained no measurable ACTH activity. One min. after injn., the level varied from 18-26 [mu]g./ml. of plasma and thereafter fell in a logarithmic fashion against time. The half time of disappearance of ACTH from plasma was 5.5 min. From the extrapolated level at zero time, it was estimated that only 6% of the injd. dose could be found in the plasma immediately after injn.