TY - JOUR T1 - Glucuronidation of Polychlorinated Biphenylols and UDP-Glucuronic Acid Concentrations in Channel Catfish Liver and Intestine JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 623 LP - 630 DO - 10.1124/dmd.107.019596 VL - 36 IS - 4 AU - James C. Sacco AU - Hans-Joachim Lehmler AU - Larry W. Robertson AU - Wenjun Li AU - Margaret O. James Y1 - 2008/04/01 UR - http://dmd.aspetjournals.org/content/36/4/623.abstract N2 - Polychlorinated biphenylols (OH-PCBs) are potentially toxic polychlorinated biphenyl metabolites that can be eliminated by glucuronidation, catalyzed by UDP-glucuronosyltransferases (UGTs). OH-PCBs with a 3,5-dichloro-4-hydroxy substitution pattern have been detected in blood from humans and wildlife, suggesting slow elimination. In this study we assessed the glucuronidation of 4-OH-PCBs with zero, one, or two chlorine atoms flanking the 4-hydroxyl group and zero to four chlorine atoms in the aphenolic ring in microsomes from channel catfish liver and proximal intestine. Product formation was quantitated with [14C]UDP-glucuronic acid (UDPGA). Physiological concentrations of UDPGA were measured in preparations of liver and intestine. When the OH-PCB concentrations were varied in the presence of saturating UDPGA concentrations, glucuronidation Vmax values were higher in hepatic than in intestinal microsomes (0.40–3.4 and 0.12–0.78 nmol/min/mg of protein, respectively), whereas the Km values were generally lower for intestine (0.042–0.47 mM) than for liver (0.11–1.64 mM). In both tissues Vmax values with 3,5-dichloro-4-OH-PCBs were lower than with the corresponding 3-chloro-4-OH-PCBs. Varying the UDPGA concentrations in the presence of saturating concentrations of OH-PCB showed that the Km for UDPGA was lower in intestine (27 μM) than in liver (690 μM). The measured concentration of UDPGA in catfish liver (246–377 nmol/g) was lower than the Km for UDPGA, suggesting that in vivo rates of glucuronidation may be suboptimal, whereas in intestine the measured UDPGA concentration (71–258 nmol/g) was higher than the Km for UDPGA. Although liver has a greater glucuronidation capacity than proximal intestine, the properties of intestinal UGTs in channel catfish enable them to efficiently glucuronidate low concentrations of OH-PCBs. ER -