Intranuclear Metabolism of Progesterone-1,2-3H in the Hen Oviduct

The metabolism of progesterone-1,2-3H has been studied in the estrogen-primed pullet. Following the intravenous administration of the hormone, radioactivity was recovered within 5 min in oviduct magnum, and at all time intervals up to 1 hour approximately one-fourth of the magnum radioactivity was localized within the nuclei of this tissue. Although the metabolism of progesterone-3H to a variety of metabolites is rapid in all tissues studied, progesterone itself and its 5α-reduced derivative allopregnanedione are the principal compounds identified in magnum cytoplasm and the only labeled steroids recovered from oviduct nuclei. The conversion of progesterone to allopregnanedione was shown to take place in magnum nuclei, and this metabolite of progesterone was recovered in significant amounts only in the magnum and shell gland of the oviduct, the comb, and the brain following the intravenous administration of progesterone-1,2-3H. At all times studied progesterone itself is the predominant species (80% or greater) bound to nuclei obtained from the magnum, whereas allopregnanedione is the principal radioactive steroid bound to nuclei in the shell gland of the oviduct.