The simultaneous measurement of aldosterone, cortisol, and corticosterone in human peripheral plasma by displacement analysis.

Abstract

Abstract A method has been designed for measuring aldosterone, cortisol, and corticosterone in a single extract of human peripheral plasma. After separation and purification by paper chromatography, the aldosterone and corticosterone are measured by radioimmunoassay employing antibodies developed in the sheep, and the cortisol by a protein-binding technique. The over-all recoveries after extraction and chromatography are aldosterone 61 ± 11 S.D. per cent, cortisol 65 ± 6.8 S.D. per cent, and corticosterone 49 ± 9 S.D. per cent. High specificity in the method is achieved by using antibodies which cross react to a very minor extent with other steroids, and by employing experimental procedures which produce consistently low blank values. The blank values for cortisol and corticosterone are indistinguishable from zero, and values for aldosterone are 2 ± 2 S.D., and 6.9 ± 0.94 S.D. picograms for water and adrenalectomized plasma, respectively. In accuracy studies, the correlation coefficients between the amount of steroid added to water and plasma and the amount recovered were 1.02, 1.03, and 0.98 for aldosterone, corticosterone, and cortisol, respectively, indicating no systematic error in the method. The method has high specificity, good accuracy, and precision and is inexpensive and technically simple to operate.