||Effect of Pretreatment on the Biliary Excretion of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin, 2,3,7,8-Tetrachlorodibenzofuran, and 3,3',4,4'-Tetrachlorobiphenyl in the Rat.
||Health Effects Research Lab., Research Triangle Park, NC. Environmental Toxicology Div. ;ManTech Environmental Technology, Inc., Research Triangle Park, NC. ;Duke Univ., Durham, NC. School of the Environment. ;North Carolina Univ. at Chapel Hill.
The laterally halogenated chemicals 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 3,3',4,4'-tetrachlorobiphenyl (TCB) exhibit the same spectrum of toxic effects as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototype and most toxic member of the halogenated aromatic hydrocarbon family. The biliary elimination of TCDF, TCDD, and TCB was examined as an indirect measure of metabolism. Male F344 rats were anesthetized with pentobarbital, the bile duct was cannulated, and 0.1 micromol (3H)TCDD, (14C)TCDF, or (14C)TCB/kg body wt was administered iv. To determine if TCDF was able to induce its own metabolism in vivo, a single dose of 1.0 micromol TCDF/kg was administered to rats by oral gavage 3 days prior to iv injection of 0.1 or 0.3 micromol (14C)TCDF/kg. Biliary excretion and hepatic concentrations of (14C)TCDF were significantly increased in the pretreated animals. These results suggest an autoinduction of TCDF metabolism.