Interconversion of 16-epioestriol and oestriol by avian liver tissue in vitro.

1. [16-(14)C]16-Epioestriol and [6,7-(3)H(2)]oestriol were incubated both simultaneously and separately at 40 degrees with hen liver homogenates obtained from birds in the laying stage. 2. Purification and identification of products was made by ether extraction, Girard separation, Celite partition and paper chromatography and crystallization to constant specific activity both with and without derivative formation. Percentage conversions of the radioactive 16-epioestriol and oestriol were calculated from these specific activities. 3. Oestriol yielded 16-epioestriol as early as 5min. after exposure of steroid to the tissue. No production of oestriol from 16-epioestriol was detectable in this time. 4. Considerably more 16-epioestriol was formed from oestriol than oestriol by the reverse reaction after 90min. of incubation. 5. 16-Oxo-oestradiol-17beta appeared in all cases to be the major identified intermediate in the interconversion of 16-epioestriol and oestriol.