Metabolism of 2,4',5-trichlorobiphenyl: tissue concentrations of methylsulphonyl-2,4',5-trichlorobiphenyl in germfree and conventional mice.

Whole-body autoradiography of 2,4',5-[14C]trichlorobiphenyl ([14C]triCB) indicated that, whereas there was accumulation of radioactivity in the tracheobronchial mucosa of conventional (C) mice 1-7 days after injection, no such effect was observed in germfree (GF) mice 1 day after injection. At days 4 and 7 there was a low, but significant, uptake by the tracheobronchial mucosa of the GF mice. Chemical analysis showed that the concentrations of 4-methylsulphonyl-triCB (4-MeSO2-triCB) in lung, kidney and liver 7 days after administration of triCB were 6.5, 14.7 and 3.7 times higher, respectively, in C than in GF mice. The results are interpreted as indicating the existence of a major metabolic route to triCB methyl sulphones involving the intestinal microflora, and a minor route, not requiring the flora.