Radioimmunoassay of Plasma Corticosterone

Abstract
This report describes a radioimmunoassay method for the measurement of unconjugated corticosterone (B) in plasma. Utilizing an anti-Cortisol antiserum cross reacting with B combined with a one step celite microcolumn chromatographic system, we have measured this latter steroid accurately in small aliquots of plasma from both male and female subjects. The plasma levels of B obtained by this method agreed well with levels observed in adult men and women, using other techniques. During a menstrual cycle studied, wide fluctuations were observed with levels ranging from 1, 3 to 14, 4 ng/ml. Adrenal suppression decreased the levels of B below 1 ng/ml. The mineralocorticoid B is predominantly ACTH -dependent.