Metabolism of [3H]oestrone sulphate by fetal membranes, placenta and uterine tissues from pregnant rabbits.

The distribution of radioactivity within the fetal membranes and uterine tissues from pregnant rabbits after an intra-amniotic injection of [3H]oestrone sulphate was determined, and the conversion to oestrone and oestradiol-17 beta during in-vitro incubation of these tissues with [3H]oestrone sulphate was measured. After intra-amniotic injection, radioactive oestrone and oestradiol-17 beta were recovered from amniotic fluid, amnion, placenta, decidua and myometrium of the injected fetus, and, in some experiments, from tissues of an adjacent fetus. During incubation, extensive metabolism of oestrone sulphate occurred in placenta and chorion, and oestrone sulphatase and 17-oxidoreductase activities were found in these tissues as well as in amnion, decidua and myometrium. We suggest that oestrone sulphate, present in amniotic fluid, may be accessible for metabolism to unconjugated oestrogen by several intrauterine tissues of the pregnant rabbit.