Prediction of metabolic clearance of bisphenol A (4,4 '-dihydroxy-2,2-diphenylpropane) using cryopreserved human hepatocytes

This study investigated the kinetics of glucuronidation of bisphenol A (BPA; 4,4'-dihydroxy-2,2-diphenylpropane) in cryopreserved human hepatocytes (HCs). Incubation conditions were developed using Sprague-Dawley rat HCs. For determination of the kinetic constants of BPA glucuronidation rates with human HCs, viable HCs (0.125 x 10(6)) were incubated with [(14)C]BPA (1.3-52 microM) for 10 min. The glucuronidation reaction demonstrated Michaelis-Menten kinetics and yielded a mean K(m) for males and females of 9 +/- 3 and 8 +/- 2 microM, respectively. The V(max) values of these reactions were 438 +/- 129 pmol/min/10(6) for male HCs and 480 +/- 208 pmol/min/10(6) for female HCs. The scaled intrinsic clearance (CL(int)) for male human HCs was 149 +/- 67 ml/min/kg (range 53-246) and for female HCs was 165 +/- 89 ml/min/kg (range 73-336). Overall, there are no apparent gender differences in the glucuronidation of BPA. These CL(int) values were then extrapolated to estimate total hepatic metabolic clearance (CL(met)) using a nonrestrictive well stirred model. The estimated CL(met) value for both male and female HCs was 6 ml/min/kg, which represents 30% of hepatic blood flow. Thus, in vivo clearance seems to depend highly on plasma protein binding. These in vitro results correlate well with in vivo studies in humans, which report extensive glucuronidation of BPA.