The relative abilities of TCDD and its congeners to induce oxidative stress in the hepatic and brain tissues of rats after subchronic exposure

The abilities of single doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to induce oxidative stress in hepatic and some extra-hepatic tissues of an imals, are well documented. In this study we have investigated the inductio n of oxidative stress in hepatic and brain tissues of rats after subchronic (13 weeks) exposure to TCDD and two of its congeners, namely 2,3,4,7,8-pen tachlorodibenzofuran (PeCDF) and 3,3',4,4',5-pentachlorobiphenyl (PCB126). TCDD, PeCDF and PCB126 were administered daily to groups of rats at various doses, for 13 weeks, and biomarkers of oxidative stress, including the pro duction of superoxide anion, lipid peroxidation and DNA-single strand break s (SSBs), were determined in the hepatic and brain tissues at the end of th e exposure period. The three congeners caused dose-dependent increases in t he production of superoxide anion, lipid proxidation and DNA-SSBs, with max imal effects achieved at doses ranging between 10-100, 20-92, and 300-550 n g/kg per day for TCDD, PeCDF and PCB126, respectively. The doses that produ ce 50% of maximal responses by each of the xenobiotics in the hepatic and b rain tissues were found to be within the ranges of 7-34, 13-32, and 137-400 ng/kg per day for TCDD, PeCDF and PCB126, respectively. The results of the study suggest that subchronic exposures to TCDD, PeCDF and PCB126 induce s ignificant oxidative damage in the hepatic and brain tissues of rats, with more damage observed in the brain as compared to the hepatic tissues. Also, as inducers of oxidative stress in the hepatic and brain tissues, TCDD is the most potent among the three congeners and PCB126 being the least potent . (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.