Conversion of testosterone and progesterone to oestrone by the ovary of the rat embryo in organ culture.

Ovaries from 19- and 20-day old rat embryos were cultured in the presence of [3H]testosterone and [3H]progesterone respectively, and the conversion of these precursors into [3H]oestrone and [3H]oestradiol was studied. By adding tracer amounts of [14C]oestrone and [14C]oestradiol to the culture media at the beginning of the analysis and crystallizing oestrone and oestradiol to constant specific activity, a conversion percentage could be calculated. There was no oestradiol formation either from progesterone or from testosterone. Oestrone was formed in measurable amounts from both precursors. It is concluded that in the ovary of the 19-20-day old rat embryo 17 beta-hydroxysteroid dehydrogenase favors the formation of oestrone.