The metabolism of some pentachlorodibenzofurans in the rat.

Three pentachlorodibenzofurans (23478-, 12378- and 12348-penta-CDF) were prepared by isomer-specific syntheses and administered to bile duct-cannulated rats in single oral doses. All three compounds were metabolized and metabolites excreted in the bile. Metabolites were identified by g.l.c.-mass spectrometry after clean-up and methylation of bile samples. Phenolic metabolites (identified as methyl ether derivatives) were formed from all three penta-CDFs by aromatic hydroxylation or by hydrolytic dechlorination. Cleavage of the ether bond with formation of a biphenyl derivative was observed with 23478-penta-CDF; from this compound small amounts of a sulphur-containing metabolite were also formed. All three penta-CDFs followed a common metabolic pathway but differed in the distribution of the metabolites. 12348-CDF was biotransformed more efficiently than the two other isomers. Unmetabolized penta-CDFs were also excreted in the bile.