The metabolism of progesterone by animal tissue in vitro. 2. Factors influencing the metabolism of progesterone by rabbit liver and the investigation of the products of metabolism

Abstract

It was demonstrated that rabbit liver contains an enzyme system able to metabolize progesterone in vitro. Metabolism is increased by addition of diphosphopyridine nucleotide and nicotinamide or of citrate to the reaction mixture; it is not inhibited under anaerobic conditions. In a large scale experiment in which progesterone was incubated with a suspension of disintegrated liver with added nicotinamide and citrate, 33% of the added steroid was accounted for by the isolation of 5 alpha-pregnane-320-dione, the 3 alpha and 3 beta-hy-droxy-alpha-pregnan-20-ones, 3 alpha-hydroxy-5 beta-pregnan-20-one, 5 beta-pregnane-3 alpha:20 alpha-diol and unchanged progesterone. In view of the complexity of progesterone metabolism, the results of urinary "pregnanediol" determinations must be interpreted with great caution.