Abstract
Abstract
A radioisotopic assay for the cytoplasmic deoxycorticosterone sulfotransferase activity (DSA) of rat liver was developed herein. Deoxycorticosterone inhibits the enzyme reaction strongly. For reliable, quantitative results, a complex assay method, using several different deoxycorticosterone concentrations, each studied with four different amounts of enzyme, was necessary. This “mosaic” assay compensated for variations of the enzyme activity observed in male and female rats. The results obtained demonstrated that cytosols from female rats contained five to six times the DSA found in males. The hepatic DSA was examined further by DEAE-Sephadex A-50 fractionation. One peak of enzyme activity was observed in cytosols from males and two peaks of enzyme activity were observed in cytosols from females. Comparison of these DSA peaks with the glucocorticoid sulfotransferases (STI, STII, and STIII) already fractionated in this laboratory, suggested that the single peak of DSA in males and the second peak of DSA eluting from DEAE-Sephadex A-50 columns in females were STIII. The first peak of DSA eluting from the ion-exchange columns in females appeared to be a new enzyme.
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