TRANSCORTIN: A CORTICOSTEROID-BINDING PROTEIN OF PLASMA. V. IN VITRO INHIBITION OF CORTISOL METABOLISM*

Abstract

In an in vitro system, employing either human or rat liver microsomes, transcortin competes efficiently for cortisol with the enzyme systems responsible for the reduction of the steroid, resulting in lesser metabolism of cortisol in the presence of transcortin. The addition of transcortin-rich plasma (pregnancy, estrogen-treated subjects) to the incubation gave results similar to those obtained with purified transcortin. The partial purification of the latter is described. The results obtained bear on the interpretation of the effects of transcortin on cortisol metabolism in vivo.