Considerations of delta 5-pregnenediol formation in ovarian tissue

20Alpha-Hydroxypregn-4-ene-3-one (20alpha-DHP) in ovarian tissue could be formed directly from progesterone (Pathway 1) or from pregnenolone via a delta 5-intermediate, pregn-5-ene-3beta, 20alpha-diol (Pathway 2). The participation of Pathway 2 is demonstrated to the extent that pregnenediol can be formed from pregnenolone and that the delta 5-diol, in turn, can be a precursor to 20alpha-DH P in vitro, using ovarian tissue from cycling rats by both flask incubation and superfusion techniques. Pathway 2 would allow greater flexibility and local regulation with respect to potential steroid sulfate conjugates of delta 5-3beta-OH intermediates. The existence of two pathways leading to 20alpha-DH P could explain the occurrance of variable levels of this steroid without a necessary direct or inverse relationship to progesterone secretion levels at different stages of the estrous cycle.