THE IN VITRO ADRENAL RESPONSE TO CORTICOTROPIN SUBTYPES: AN IMPROVED ASSAY DESIGN

Abstract

An eight point assay design for assessment of corticotrophin potency in terms of any standard corticotrophin is described. Each point can be repeated four times by using littermate rat adrenal tissue. The response of isolated adrenal tissue to corticotrophin stimulation is measured in terms of the corticoids produced. As many as three unknown samples may be measured in terms of one standard or compared with one another. Three subtypes of corticotrophin have been assessed in one assay design. They are acid extracted crude corticotrophin (represented by the original U.S.P. Provisional Reference Standard), glacial acetic acid extracted, and oxycel purified corticotrophin. All these corticotrophins showed the same dose–response characteristics and relative potencies in agreement with the Sayers ascorbic acid depletion assay by the intravenous route. When three different samples were assayed in one design of 32 rats the average lambda was 0.18, and the limits of error for each sample were approximately ± 45%.