Estrogenic properties of 3,9-dihydroxy-7,12-dimethylbenz[a]anthracene in rats

Previously, the 3,9-dihydroxy derivative of benz[a]-anthracene was shown to be weakly estrogenic. The availability of the related diol of the mammary carcinogen dimethylbenz[a]-anthracene, i.e., 3,9-dihydroxy-7,12-dimethylbenz[a]anthracene (3,9-diOHDMBA), prompted a similar study of its estrogenic properties. The competitive binding studies of 3,9-diOHDMBA with 17beta-estradiol in the uterine cytosol of immature SD rats gave a Ka of 1.7 x 10(8) M-1. 17beta-Estradiol (10(-9) M) binding to the 8S binding protein was inhibited by 3,9-diOHDMBA at concentrations similar to those of nafoxidine HCl (1 x 10(-5) M). Bioassay demonstrated that the diol possesses 1/4,464 the activity of 17beta-estradiol.