In vitro and in vivo estrogenic activity of chlorinated derivatives of bisphenol A.

The estrogenic activity of bisphenol A (BPA) and its chlorinated derivatives, 2-(3-chloro-4-hydroxyphenyl)-2-(4-hydroxyphenyl)propane (3-ClBPA) and 2,2-bis(3-chloro-4-hydroxyphenyl)propane (3,3'-diClBPA) was assessed by determining their relative binding affinity for the human estrogen receptor-alpha and -beta (ERalpha and ERbeta) and also their uterotrophic activity in ovariectomized female rats. BPA and its chlorinated derivatives were active in competing with [3H]17beta-estradiol for their binding to the human ERalpha and ERbeta proteins. While 3-ClBPA and 3,3'-diClBPA competed more effectively for ERalpha binding than BPA (IC50 values of 2.48x10(-5), 1.28x10(-5), and 1.08x10(-4)M, respectively), they had similar activity as BPA for competing the binding to ERbeta (IC50 values of 1.43x10(-5), 1.87x10(-5), and 2.59x10(-5)M, respectively). To determine the uterotropic activity, three doses (10, 50 and 100 mg/kg/day) of BPA and its derivatives were given to mature ovariectomized Sprague-Dawley rats for 3 consecutive days. Treatment of animals with 50 and 100 mg/kg/day of BPA or its chlorinated derivatives caused a significant increase in the uterine wet weight and the endometrial area. The results of our present study demonstrated that the affinities of 3-ClBPA and 3,3'-diClBPA for ERalpha were higher than the affinity of BPA, although the in vivo estrogenic activity of the two chlorinated BPAs in ovariectomized female Sprague-Dawley rats appeared to be comparable to that of BPA.