OCCURRENCE OF 19-OXOANDROST-4-ENE-3,17-DIONE IN THE COURSE OF OESTROGEN BIOSYNTHESIS BY EQUINE TESTICULAR MICROSOMES

Abstract

ABSTRACT Radioactive 19-oxoandrost-4-ene-3,17-dione was obtained as one of the metabolites produced from the 14C-labelled androstenedione and 19-hydroxy-androst-4-ene-3,17-dione by equine testicular microsomes (10 000–105 000 × g precipitate) under an aerobic condition. Under an anaerobic condition, however, the production of 19-oxoandrostenedione and oestrone from the above two precursors was severely reduced. Identification of 19-oxoandrostenedione was based on the following criteria: 1. Mobilities of the metabolite were identical with those of authentic preparation of 19-oxoandrostenedione on thin layer chromatograms developed in several different solvent systems. 2. Other physico-chemical characteristics of the metabolite such as ultraviolet absorption spectrum, and behaviour against chemical reagents were similar to those of authentic 19-oxoandrostenedione. 3. Specific activities of the crystal and the solid in mother liquor were found to be constant, when the 14C-labelled metabolite was repeatedly crystallized with authentic 19-oxoandrostenedione. 4. Moreover, when the 14C-labelled metabolite was recrystallized with authentic 3H-labelled 19-oxoandrostenedione, ratios of the two radioisotopes of the crystal and the solid in mother liquor were constant. The time course of the metabolism of androstenedione and 19-hydroxyandrostenedione revealed that the metabolic fate of 19-oxoandrostenedione had characteristics compatible with an intermediate in the oestrone synthesis from the above two precursors. The role of this particular metabolite was discussed in relation to the oestrogen synthesis in the equine testicular tissue.