Biochemical and toxicological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) congeners in female rats

Abstract

The capability of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)² and six congeners to induce toxic and biochemical changes in rats was investigated. In addition to TCDD, the following compounds were administered at a dose of 40 or 400 μg/kg/day for three days P.O.: 2,7-dichlorodibenzo-p-dioxin (DCDD); 1,2,4-trichlorodibenzo-p-dioxin (TrCDD); 1,2,3,4-tetrachlorodibenzo-p-dioxin; l,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin; 3,3′,4,4′,5-pentachlorobiphenyl (PCB); and 2,2′,4,4′,5,5′-hexachlorobiphenyl (HCB). Six days after treatment the animals were killed. Lipid peroxidation and glutathione peroxidase (GSH-PX) activity were determined in liver and kidney. Hepatic aryl hydrocarbon hydroxylase (AHH) activity was determined 48 hr following the administration of 400 μg/kg of each congener or 40 μg/kg of TCDD. With the exception of PCB and TCDD, the other congeners produced no toxic or biochemical changes at the doses given as determined by the above parameters. PCB (400 μg/kg) resulted in a 4-fold increase in lipid peroxidation and a 69% decrease in GSH-PX activity. These results were comparable to the effects of a 40 μg/kg dose of TCDD. PCB treatment resulted in a 80% decrease in thymus weight, and a 3.8-fold increase in AHH activity which were comparable to the effects of TCDD. A correlation appears to exist between the ability to induce hepatic AHH activity, enhance lipid peroxidation. inhibit GSH-PX activity, and decrease body and thymus weights.