The adsorption of corticosteroids to particulate preparations of rat liver

Abstract

Various cell fractions were isolated from homogenates of rat liver in 0.9% NaCl by differential centrifuging. The distribution of radioactivity derived from injected corticosteroids between the cell fractions was found to be the same as the distribution of [C14]corticosteroids added to homogenates from normal rats. The particle fraction that sedimented at the highest centrifugal force contained the greatest concentration of hormone, but the steroid was not confined to any one fraction of the cell. The steroid hormones were more strongly bound to the cell particles than their polar metabolites. A comparison of the distribution of radio-activity between the particulate fraction of various tissues and the supernatant solution showed that liver had the greatest capacity for adsorbing corticosteroids. Pretreatment of the cell particles, which leads to the removal of ribonucleic acid, did not affect the adsorption of corticosteroids. Twenty-four hours after a single injection of 5 mg. of [Cl4]corticosterone into normal rats, which brought about an increase in liver glycogen, about 0.1% of the administered radioactivity was found in the liver as unchanged hormone. The results suggest that the long-term effect of hormonal steroids is linked with their adsorption to proteinaceous cell structures, where they are relatively inaccessible to enzyme action.