Received for publication January 24, 2007.
Revised July 19, 2007.
Accepted for publication July 20, 2007.

Prediction of Metabolic Clearance of Bisphenol A using Cryopreserved Human Hepatocytes

Abstract

This study investigated the kinetics of glucuronidation of Bisphenol A in cryopreserved human hepatocytes (HC). Incubation conditions were developed using Sprague Dawley rat HC. For determination of the kinetic constants of BPA glucuronidation rates with human HC, viable HC (0.125 X 10⁶) were incubated with [¹⁴C]- BPA (1.3-52 µM) for 10 min. The glucuronidation reaction demonstrated Michaelis-Menten kinetics and yielded a mean Km for males and females of 9 ± 3 and 8 ± 2 µM, respectively. The Vmax of these reactions were 438 ± 129 picomoles/min/10⁶ for male HC and 480 ± 208 picomoles/min/10⁶ for female HC. The scaled intrinsic clearance (CL_int) for male human HC was 149±67 ml/min/kg (range 53-246) and for female HC 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 non-restrictive well stirred model. The estimated CL_met value for both male and female HC was 6 ml/min/kg, which represents 30 % of hepatic blood flow. Thus, in vivo clearance appears 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.

Key words: hepatocytes, in vitro-in vivo scaling