Characteristics of the binding component for testosterone and androstenedione in rat liver cytosol.

A study was made of the nature of a macromolecular component in the hepatic cytosol of male rats which binds with testosterone and androstenedione. The saturation analysis revealed that this component has binding affinity with these androgenic steroids and a limited number of binding sites. This component was inactivated by incubation with proteolytic enzymes and by heating, but was unaffected following incubation with RNase. Analysis by sucrose density gradient centrifugation revealed that this component had a sedimentation coefficient of approximately 10 S. On the basis of the elution profile of the component on gel chromatography, the molecular weight and the similarity of the structure of these androgens, it seems most likely that one binding component is responsible for both testosterone and androstenedione. It was postulated that the only difference in binding for these androgens is that testosterone, showed a more rapid association rate with this component, than androstenedione