IDENTIFICATION AND CHARACTERIZATION OF CYTOSOLIC SULFOTRANSFERASES INNORMAL HUMAN ENDOMETRIUM

Understanding the factors which alter estrogen metabolism and activity in endometrial tissue is important because unopposed estrogen stimula tion is an important risk factor in the development of endometrial car cinoma. The cyclic progression of the endometrium through proliferativ e and secretory phases is normally under the control of the ovarian ho rmones beta-estradiol (E-2) and progesterone. One mechanism by which p rogesterone inhibits the activity of E-2 in secretory endometrium is b y elevating the degree of E-2 sulfation, thereby reducing its ability to bind to the estrogen receptor and elicit a cellular response. Our l aboratories have investigated the cytosolic sulfotransferases (STs) fo und in biopsies of both proliferative and secretory endometrium obtain ed from five normal pre-menopausal women who were not taking any drugs or steroids. Two of the human cytosolic STs were detected in human en dometrial tissues. The phenol-sulfating form of phenol ST (P-PST) was found at varying levels in cytosol from both proliferative and secreto ry endometrium in all of the women studied but with no consistent corr elation to the phase of the menstrual cycle. In contrast, estrogen ST (EST) was not detected in the proliferative endometrial cytosol of any of the women studied but was consistently found in all of the secreto ry endometrial cytosols. The presence and levels of these STs was conf irmed by ST activity studies, immunoblot analysis and Northern blot an alysis. These results indicate that the expression of EST in human end ometrial tissues varies with the phase of the menstrual cycle and is m ost likely regulated by progesterone secreted from the ovaries. (C) 19 98 Elsevier Science Ireland Ltd. All rights reserved.