Hydrolysis of estrone sulfate in uterine minces of the 6-days pregnant rat.

In view of the possible participation of estrogen 3-sulfoconjugates in reproductive events, such as reproductive cycles, gestation and parturition, an experiment was carried out where the conversion of labeled estrone sulfate ([3H]E1S) to estrone ([3H]E1) was measured during in vitro incubation with minced uterine tissues representing implantation sites (IS) and non-implanted areas (NIS), from pregnant rats at the time of blastocyst implantation. Significant hydrolysis of the 3-sulfate, by the action of the estrogen sulfatase, was found in both tissues being less in IS than in NIS, when expressed either as pmol of E1 formed/mg wet tissue/h (238 +/- 37 vs 337 +/- 15, respectively) or as pmol of E1 formed/mg protein/h (1278 +/- 198 vs 1773 +/- 81). Both differences are statistically significant at the 0.001 level. The results obtained here suggest that E1S present in uterine fluids may be taken up and hydrolyzed by the sulfatase present in both intrauterine tissues of the 6-days pregnant rat. However, the decreased formation of E1 found in IS suggests that rat blastocyst is able to regulate the local concentration of unconjugated estrogens required at IS by modulating the activity of the estrogen sulfatase.