Mutagenic activation of tris(2,3-dibromopropyl)phosphate: the role of microsomal oxidative metabolism.

The flame retardant tris(2,3-dibromopropyl)phosphate (Tris-BP) is converted to products which are mutagenic for Salmonella typhimurium TA 100 in the presence of rat liver microsomes, NADPH and oxygen. Other bromopropyl-compounds were also mutagenic; 2,3-dibromopropene and 2,3-dibromopropionic acid were directly mutagenic, whereas 2,3-dibromopropanol and tris(2-bromopropyl)phosphate were weakly mutagenic after addition of liver microsomes and cofactors. Typical in vivo and in vitro inhibitors of cytochrome P-450 inhibited Tris-BP mutagenicity. The effects of inducers of cytochrome P-450 on Tris-BP mutagenicity was dependent on the concentration of mutagen and microsomal protein in the assay, indicating complexity in the kinetics involved when dealing with possible multiple pathways that lead to mutagenicity. Addition of glutathione strongly inhibited Tris-BP mutagenicity. It is suggested that Tris-BP is oxidized to a reactive electrophile, possibly the 2-keto derivative, which could react with nucleophilic groups in DNA and thus lead to mutagenic events.