Hepatic metabolism of chlorinated derivatives of bisphenol A (ClxBPA) and interspecies differences between rats and humans

Abstract

During chlorination treatments of drinking water, aqueous bisphenol A (BPA) can react with chlorine to form chlorinated derivatives of BPA (mono, di, tri and tetra-chlorinated derivatives) or ClxBPA. These emerging substances are endocrine disruptors associated with obesity, type II diabetes (TD2M) and myocardial infarction. ClxBPA are present in different human biological matrices but their toxicokinetics remain unknown. The aim of this study was to measure and compare the metabolic kinetics in the liver of four ClxBPA (ClBPA, Cl2BPA, Cl3BPA and Cl4BPA) between compounds and between species (Sprague-Dawley rats vs humans). To estimate their metabolic constants (Vmax, Km, Intrinsic clearance), metabolic assays were performed in hepatocyte suspensions. Assays revealed that metabolic constants of ClxBPA can greatly vary depending on substances and species. While ClBPA and Cl2BPA show similar unbound intrinsic clearances (ClintU) in rat incubation media, values for Cl3BPA and Cl4BPA are very different (3.109 and 0.684mL/min/106 hepatocytes, respectively). Unlike in rats, human results are quite different as Cl3BPA and Cl4BPA have similar unbound intrinsic clearances, while ClBPA and Cl2BPA diverge (0.350 and 1.363mL/min/106 hepatocytes, respectively). In both species, Cl2BPA and Cl3BPA have relatively similar clearances, and ClBPA is very different from Cl4BPA. Although we quantified the proportion of sulfo- and glucurono-metabolites, other metabolites may have been formed (e.g., glutathione, disulfate, or oxidative metabolites). This study showed that chlorination had an impact on hepatic intrinsic clearance of ClxBPA in rats and humans and measured values will be valuable for the development of PBPK models for use in exposure assessment.