6-nitro-1,3,8-trichlorodibenzofuran (6-NCDF): A new partial estrogen

Treatment of immature female Sprague-Dawley rats with 6-NCDF caused a dose-response increase in rat uterine weight 48 hours after treatment. At a dose of 25 μmol/kg the uterotrophic effects of 6-NCDF and 17β-estradiol (5 μg/rat x 2) were comparable. 17β-estradiol also causes a significant increase in rat uterine cytosolic and nuclear estrogen and progesterone receptor levels whereas 6-NCDF significantly increased only the cytosolic progesterone receptors in the rats. In contrast, 17β-estradiol cause approximately a 100% increase in rat uterine peroxidase activity whereas 6-NCDF, like 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) caused a > 50% decrease in this response compared to (vehicle) control-treated animals. 6-NCDF competitively displaced [3H]-TCDD from the uterine cytosolic Ah receptor but did not exhibit affinity for either the uterine estrogen or progesterone receptor. The data and other results suggest that the estrogenic effects of 6-NCDF may be mediated through the Ah receptor