DNA DOUBLE-STRAND BREAKS AND APOPTOSIS AFTER IN-VITRO EXPOSURE TO TOLUENE DIISOCYANATE

The immediate effect of toluene diisocyanate (TDI) on genomic DNA of s heep and rabbit white blood cells has been investigated. Following the treatment of sheep blood by TDI, the isolated DNA was analysed by ani on exchange chromatography (FPLC) and melting behaviour before and aft er denaturation. The results of FPLC indicated that TDI induces DNA do uble-strand breaks in sheep white blood cells. Following denaturation of TDI-treated DNA, the results demonstrated that at least one DNA fra gment, representing about 10-20% of total DNA, is cross-linked by TDI or TDI metabolite. About 39% more of double-stranded structures are re constituted in DNA extracted from sheep white blood cells 3 hr after i ncubation with TDI. In addition, chromosomal DNA from rabbit blood was investigated with the 'agarose-plugs' method by pulsed-field gel elec trophoresis 2 hr after incubation with TDI, and the agarose gels were quantitatively evaluated with a laser densitometer. Further studies wi th prednisone were conducted to correlate these results with the pheno menon of apoptosis. The in vitro results show that TDI can induce degr adation of mitochondrial DNA and large DNA fragments, which result fro m apoptosis, to small DNA fragments.