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EVALUATION OF ORAL AND INTRAVENOUS ROUTE PHARMACOKINETICS, PLASMA PROTEIN BINDING AND UTERINE TISSUE DOSE METRICS OF BPA: A PHYSIOLOGICALLY BASED PHARMACOKINETIC APPROACH
Citation:
Teeguarden, J., J. M. Waechter, H. J. Clewell, T. Covington, AND H A. Barton. EVALUATION OF ORAL AND INTRAVENOUS ROUTE PHARMACOKINETICS, PLASMA PROTEIN BINDING AND UTERINE TISSUE DOSE METRICS OF BPA: A PHYSIOLOGICALLY BASED PHARMACOKINETIC APPROACH. Presented at Society of Toxicology Annual Meeting, New Orleans, LA, March 06 - 10, 2005.
Description:
Bisphenol A (BPA) is a weakly estrogenic monomer used in the production of polycarbonate plastics and epoxy resins, both of which are used in food contact applications. A physiologically based pharmacokinetic (PBPK) model of BPA pharmacokinetics in rats and humans was developed to provide a physiological context in which the processes controlling BPA pharmacokinetics (e.g. plasma protein binding, enterohepatic recirculation of the glucuronide, BPAG) could be incorporated. A uterine tissue compartment was implemented to allow the correlation of simulated ER binding of BPA with increases in uterine wet weight (UWW) in rats. Intravenous and oral-route blood kinetics of BPA in rats and oral-route plasma and urinary elimination kinetics in humans were well described by the model. Simulations of rat oral-route BPAG pharmacokinetics were less exact, most likely the result of over simplification of the GI tract compartment. Comparison of metabolic clearance rates derived from fitting rat i.v. and oral-route data implied that intestinal glucuronidation of BPA is significant. In rats but not humans, terminal elimination rates were strongly influenced by enterohepatic recirculation. In the absence of BPA binding to plasma proteins, high ER occupancy was predicted at doses without uterine effects. Restricting free BPA to the measured 6% demonstrated the importance of including plasma binding in BPA kinetic models. The relationship between ER occupancy and UWW increases fit expectations for a receptor mediated response with low ER occupancy at doses with no response and increasing occupancy with larger increases in UWW. (This abstract does not necessarily reflect US EPA policy.)