Cyclic Activity of Estrogen Sulfotransferase in the Gilt Uterus

Minced uteri from gilts in various days of the estrous cycle were incubated for 2 hr with l7β-estradiol-6,7-3H, (∼5 × 10−9M) and Na235SO4 (∼ l × 10−4M), and sections of the same uterine horns and the corresponding ovaries were prepared for histological examinations. When the estrogens were extracted from the incubation and separated into unconjugated and sulfated fractions, it was found that sulfation varied with the day of the cycle. At estrus and in the immature animal there was no sulfation of estrogens. Estrogen sulfotransferase activity began to appear at metestrus (day 3) and at diestrus (day 6) rose sharply to a peak level around day 9 (80% of the labeled estrogen sulfated). Although the unconjugated fraction contained predominantly 17β-estradiol, most of the conjugated fraction consisted of estrone sulfate. Incubations carried out for various time intervals revealed a constant rate of sulfation of estrogens, previously formed estrone being the favored substrate. The proportion of the sulfate fraction due to estrone sulfate quickly reached a constant level whereas estrone in the unconjugated fraction rose more slowly. The correlation of the histological changes to the enzymic activities is discussed. (Endocrinology95: 1680, 1974)