Single antibody technique for radioimmunoassay of cortisol in unextracted serum or plasma

Abstract

A radioimmunoassay procedure for cortisol is described requiring only 5 μl of serum or plasma. Native cortisol binding proteins are denatured by heating 5 μl of sample in 0.2 ml of glutamate buffer in a boiling water bath for 15 min. After a 2 hr incubation of heat treated serum or plasma with [H3]cortisol and cortisol antibody, free and bound cortisol are separated by the use of hemoglobin coated charcoal. The method is easy and sensitive, and results compare favorably with those of a well accepted acid fluorescence method. In addition, it is shown that serum and heparinized plasma yield the same results by this method, and therefore both can be assayed by this procedure.