van den Hurk Peter, Wiley Faith E, Lavoie Emma T, Grasman Keith A, Bowerman William W
Department of Biological Sciences, Clemson University, 237 Long Hall, Clemson, SC 29634, USA.
Comp Biochem Physiol C Toxicol Pharmacol. 2007 Sep;146(3):301-7. doi: 10.1016/j.cbpc.2007.03.004. Epub 2007 Mar 14.
Little is known about the correlations between biotransformation enzymes in juvenile birds after exposure to environmental toxicants like PCBs. In this study eggs of domestic chicken (Gallus domesticus) were dosed with PCB126 in concentrations of 0.175-0.325 ng/g egg weight. Liver subcellular fractions were analyzed for activities of Phase 1 and Phase 2 biotransformation enzymes 2 and 5 weeks post-hatch. Ethoxyresorufin O-deethylase (EROD) activity was increased in both the 2-week and 5-week samples. Glutathione-S-transferase (GST) activity was increased in the 2-week samples only, but the 5-week samples showed an overall much higher GST activity, probably as a result of a still developing enzyme expression in maturing chickens. The same pattern was seen in the phenol-type UDP-glucuronosyltransferase (UGT) activity of the control animals. The week two samples showed a positive dose-response relationship for the UGT activity, but after 5 weeks this was reversed, possibly caused by inhibition of hydroxylated PCB metabolites. Phenol-type sulfotransferase (SULT) activities were not significantly correlated with time or dose. There was a strong positive regression between the Ah-receptor mediated EROD and UGT activities. The EROD activities were also positively correlated to the GST activities. Most interesting was a negative correlation between the UGT and SULT activities: an inhibited UGT activity appeared to be compensated by an increased SULT activity.
