IN VITRO BIOASSAY OF CORTICOTROPIN: MODIFICATION AND STATISTICAL TREATMENT

WE HAVE previously (Saffran and Bayliss, 1953) described an in vitro system that can be used for estimating the potency of preparations of corticotropin, but the experimental design described then did not permit statistical evaluation of the data. The procedure has been modified to allow the use of standard computational methods for the calculation of the potency, and its limits, of an unknown preparation relative to a standard. (Pugsley, 1946; Bliss, 1951). The modified method is relatively rapid and convenient to carry out and its precision compares favorably with other bioassay methods. METHOD Eight young adult rats (125 to 200 gm) of the Sprague-Dawley strain are used in each assay1. The rats are anesthetized by the intraperitoneal injection of 5 mg. of nembutal per 100 gm. of rat2. The adrenals are removed from a rat and are carefully freed of adhering fat with fine scissors, taking care that the adrenal is not damaged.