Abstract
A method is described for the quantitative assay of adrenal cortical hormones by the muscle-work test using the adre-nalectomized-nephrectomized rat. A unit of activity is defined as the work equivalent of a 0.2 mg. dose of 17-hydroxy-11-dehydrocorticosterone administered twice during the 24-hr. test. A standard dosage-response curve was set up using 17-hydroxy-11-dehydrocorticosterone which permitted the interpolation of work performance into units of the standard. The method is specific for the detection and estimation of biologic activity characteristic of the C11 oxygenated cortical steroids. Data illustrating the sensitivity and reliability of the test are presented.