STUDIES OF ADRENAL CORTICOSTEROIDS. I. ESTIMATION OF PLASMA CORTICOSTERONE AND CORTISOL*

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Abstract
A method is presented consisting of modifications of Sweat's original fluorometric technic for the estimation of corticosterone and cortisol in plasma. These modifications include substitution of ethyl acetate for chloroform as the extracting solvent, replacement of the pentane-alcohol partition step by Florisil chromatography and replacement of the mercury arc lamp for excitation light by a more monochromatic light source. These changes appear to have improved the specificity of the method. In young adults, plasma concentrations of 3.0 μg. per 100 ml. for corticostrone and 10.9 μg. per 100 ml. for cortisol were obtained. Considerable individual difference was observed when comparing the fluorometric value for cortisol with the Nelson-Samuels value for 17-OHCS. General problems remain concerning the identification and quantitation of corticosterone, as indicated by the disparity among values obtained for corticosterone in peripheral human plasma by the various methods used.