Evidence for 16beta-hydroxylation of estrogens by guinea pig liver slices

In an earlier communication, we conclusively proved that estrone-3-sulfate could be hydroxylated in the 16alpha position by guinea pig liver slices. Disulfates of 16alpha-hydroxyestrone and estriol were identified. Suggestive evidence for 6-hydroxylated metabolites was also mentioned. A careful reinvestigation has now shown that the steroid disulfate fraction is composed of 16alpha- and 16beta-hydroxylated steroids. 16beta-Hydroxyestrone in particular is an important quantitative metabolite of estradiol-17 beta. It is concluded that no firm evidence is available for the formation of 6-hydroxysteroids in the tissue system under consideration.