Enzymatic reduction of the C-20 carbonyl group of tetrahydrocortisone and 17-hydroxypregnanolone.

It is known that reduction of the carbonyl group at C-20 to a secondary hydroxyl group occurs in the course of the metabolism of progesterone and the adrenocortical hormones in man. During the past 4 years, several groups of investigators have observed this reduction when certain adrenocortical hormones or their metabolites are perfused through liver or incubated with surviving liver slices or homogenates derived from liver. It has been established chiefly from the work of Recknagel and Glenn (2) that the enzyme system which effects this reduction is largely present in the microsomes. We have studied the reduction of the carbonyl group at C-20 of pregnane30,1701,21-triol-ll , 20-dione (tetrahydrocortisone) and of pregnane-3a ,17a-diol-20-one (17-hydroxypregnanolone) in fortified, fractionated homogenates of rat liver. In this paper we wish to describe the isolation of the metabolite pregnane3cu, 17a,20/3,21-tetrol-11-one (p-cortolone) (3) after incubation of tetrahydrocortisone with such a homogenate and the isolation of the metabolites pregnane-3a, 17a, 20or-trio1 and its C-20 epimer after a similar incubation of 17-hydroxypregnanolone.