Comparative mutagenicity and toxic effects of 2,5,2',5'-tetrachlorobiphenyl and its metabolites in bacterial and mammalian test systems.

The possible toxicological properties of 2,5,2',5'-tetrachlorobiphenyl (TCB), 4-hydroxy-2,5,2',5'-tetrachlorobiphenyl (TCB-OH), and 2,5,2',5'-tetrachlorobiphenyl-3,4-oxide (TCB-oxide) were evaluated in three bioassay systems. Incubation of rat hepatocyte plasma membranes with 50 microgram/ml of TCB-OH decreased the activity of Mg2+-ATPase by approximately 90%, whereas approximately half of the enzyme activity remained after the TCB or TCB-oxide treatment. All three compounds were found to be inactive in the Salmonella/microsome mutagenicity assay. Only TCB-OH possessed potent cytotoxic activity against all four S. tymphimurium strains tested. It affects the viability of TA 1537 by as much as 40% even at concentrations as low as 1 microgram/ml. These data suggest the potential toxicological significance of metabolic activation by the hepatic microsomal mixed-function oxidases.