A Sensitive Biologic Assay for ACTH

Abstract

Fluorometric determination of corticosteroids in adrenal venous plasma of the acutely hypophysectomized rat has led to the development of 2 new techniques for the measurement of ACTH. The first, consisting of jugular injection of test material, with adrenal venous bleeding 5 minutes later, gives linearity of response to log doses of ACTH ranging from 0.05 to 1.0 milliunits (mU). The second method, consisting of retrograde injection of ACTH up the adrenal vein, with adrenal venous bleeding 90 seconds later, gives linearity of response over a range from 0.005 to 0.5 mU ACTH. The retrograde technique, while less precise, provides greater adrenal sensitivity to minute doses of ACTH than heretofore described. These methods are adaptable to the measurement of ACTH in biologic fluids.