ABSTRACT
The relation conjugated/unconjugated estrogens associated with reproductive processes has brought about the interest to study the biological role and regulation of the estrogen sulfotransferase and estrogen sulfatase which participate in the formation and hydrolysis of estrogen 3-sulfates, respectively. In this paper, both activities were measured through the reciprocal conversion of 3H-estrone sulfate and 3H-unconjugated estrogen during in vitro incubation with implantation sites (SI) and non-implanted sites (SNI) from the rat uterus, during the process of embryo implantation. Contrasting enzyme activities were found in these tissues. While sulfotransferase activity was higher in SI than in SNI (0.205 vs 0.144 pmol of E1S formed/mg protein/h, the inverse was found for the sulfatase (1.470 vs 1.977 pmol of E1 formed/mg protein/h). These results indicate the presence of both enzymes in the rat uterus and suggest the existence of a mechanism in SI that locally regulate the concentration of free and sulfoconjugated estrogens in which these enzymes participate.