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Sulfohydrolase Activity for Estrone Sulfate and Dehydroepiandrosterone Sulfate in Human Fetal Membranes and Decidua around the Time of Parturition^*

Departments of Obstetrics and Gynaecology and Biochemistry, University of Western Ontario, The Research Institute, St. Joseph's Hospital London Ontario, Canada N6A 4V2

Address all correspondence and requests for reprints to: Dr. B. F. Mitchell, Department of Obstetrics and Gynaecology, The Research Institute, St. Joseph's Hospital, 268 Grosvenor Street, London, Ontario, Canada N6A 4V2.

We examined the distribution and kinetic parameters of sulfohydrolase activity in human amnion, chorion, and decidua using estrone sulfate (E₁S) and dehydroepiandrosterone sulfate as substrates. Amnion contained low levels of sulfatase activity. Chorion had active sulfohydrolase activity for both substrates, but a significantly greater maximum velocity (V_max) for E₁S. The K_m was not different between the two substrates. However, there was a slight but statistically significant decrease in K_m and increase in V_max for sulfohydrolase activity using E₁S in chorion from patients delivering vaginally after the spontaneous onset of labor compared to those delivering by elective cesarean section before the onset of labor but at a similar gestational age.

Decidua possessed sulfohydrolase for E₁S with similar K_m and V_max as chorion. There were no changes occurring around the onset of labor. Using dehydroepiandrosterone sulfate as substrate, the decidua had a similar K_m as the chorion, but its V_max was significantly less.

In both tissues for both substrates, the enzyme had highest specific activity in the 105,000 x g pellet, with almost no activity in the soluble fraction. The greatest total sulfohydrolase activity was contained in the 800 x g pellet despite several methods of homogenization and washing of the 800 x g pellet.

We conclude that the sulfohydrolase activity of human chorion and decidua may be an important factor in regulating free steroid levels within the pregnant uterus. The significant change in the kinetic parameters of E₁S sulfatase may partially explain the increased ability of chorion to hydrolyze E₁S which occurs in association with the spontaneous onset of labor.

^* This work was supported by Grant MA-7731 from the Medical Research Council of Canada (to B.F.M.).

Received April 17, 1985.

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