The Estimation of Small Amounts of Corticosterone in Rat Plasma

Many of our investigations involving adrenal physiology have been carried out in the rat ( 14).Since corticosterone is the preponderant adrenal steroid found in rat plasma, l it became essential to develop a rapid, valid method for its determination.The Silber-Porter method ( 5) is inadequate for studies in the rat because it is neither sensitive nor specific enough.The method of Sweat (B), although demonstrating the usefulness of sulfuric acid-induced fluorescence for analysis of plasma corticosteroids, has not been found practical.Our method uses the double extraction technique of Silber and Porter and a modification of the fluorescence technique described by Sweat (7).EXPERIMENTAL