Radioimmunoassay for human corticosteroid-binding globulin.

We isolated corticosteroid-binding globulin from human plasma and used the isolated protein as the antigen in raising antibodies in rabbits. The resulting antiserum was used to develop an RIA with which we can determine the globulin in as little as 0.007 microL of serum, although we routinely use, after appropriate dilution, 0.02 microL. The mean concentration of corticosteroid-binding globulin in the serum of 40 normal subjects was 32.4 (SD 4.2) mg/L. The correlation (r) between results with this RIA and those by an established binding assay was 0.94.