Relative Potency of Xenobiotic Estrogens in an Acute in Vivo Mammalian Assay

The in vivo effects of xenoestrogens are of interest in relation to their potential health risks and/or beneficial effects on humans and animals. However, the apparent in vivo potency of the examined response can be confounded by a short half-life, and the metabolism of estrogens is very dependent on the nature of conversion and/or inactivation. To minimize such variables, we examined the estrogenic potency of a range of xenoestrogens in an acute in vivo assay-the stimulation of increased uterine vascular permeability in ovariectomized mice 4 hr after subcutaneous administration. While estradiol ( E2) and estriol ( E3; a relatively weak natural estrogen) readily induced vascular responses [median effective dose $({\rm ED}_{50})