Sulfation by guinea pig chorion and uterus: differential action towards estrone and estradiol

The activities of estrogen sulfotransferase, estrogen sulfatase and estradiol 17beta-dehydrogenase change considerably in the guinea pig uterine compartment during gestation. This study was undertaken to inquire if the chorion membrane could influence the pattern of estrogen resulting when substrates were applied to the fetal surface of the chorion while it was attached, late in gestation, to the uterine wall. This tissue system resulted in a differential handling of estrone and estradiol. Estrone was largely excluded from the tissue, remaining mainly in free steroidal form. Estradiol was considerably converted to its 3-sulfate which was mainly retained by the chorion. Parallel experiments with chorion and uterus separately failed to discriminate between the two substrates. Hydrolysis of estrone sulfate and estradiol 3-sulfate was similar in all three tissue systems. It appears that the interaction of chorion with uterus late in gestation causes a difference in tissue action towards the two steroid substrates of closely related structure. The results suggest a limitation in tissue uptake of estrone compared with estradiol, or a much greater sulfotransferase activity towards estradiol. Whole cytosols of late gestational chorion catalyzed sulfation of estradiol at about double the velocity of estrone. This may only partly account for the difference in the intact chorion-uterine tissue system.