MUTAGENICITY OF VINYL-CHLORIDE AND ITS REACTIVE METABOLITES, CHLOROETHYLENE OXIDE AND CHLOROACETALDEHYDE, IN A METABOLICALLY COMPETENT HUMAN B-LYMPHOBLASTOID LINE

Vinyl chloride (VC), a known human and rodent carcinogen, is metabolic ally activated by cytochrome P450 to chloroethylene oxide (CEO), which can rearrange to chloroacetaldehyde (CAA) or undergo hydrolysis. To f urther understand the roles of CEO and CAA in VC mutagenesis, the type s and frequencies of mutations induced at the hypoxanthine (guanine) p hosphoribosyl-transferase (hprt) locus were examined in a human B-lymp hoblastoid line constitutively expressing human cytochrome P450 2E1 (H 2E1 cells), VC was toxic and mutagenic to H2E1 cells as a function of incubation time; exposure to 7.5% VC in air resulted in 75% survival a nd an hprt mutant frequency of 42x10(-6) after 48 h, compared to 5.7+/ -2.7x10(-6) for unexposed cells, The exposure of H2E1 cells to 0.8 to 15.0% VC in air produced similar mutant frequencies without a clear do se-response relationship, suggesting saturation of metabolic activatio n, Both CEO and CAA exhibited dose-dependent increases in cell killing and mutant frequency in H2E1 cells, Treatment with 16 mu M CEO for 24 h resulted in 75% survival and an induced mutant frequency of 23x10(- 6), while 16 mu M CAA produced 5% survival and an induced mutant frequ ency of 20x10(-6), Structural alterations at the hprt locus in indepen dent thioguanine-resistant clones were examined by Southern blot analy sis of Pst I-digested DNA with a full-length human hprt cDNA probe, Te n percent (5/50) of VC-induced and 18% (7/38) of CEO-induced mutants s howed detectable deletions, compared with 45% (9/20) of CAA-induced mu tants, Thus, VC and CEO displayed similar toxicity/mutation profiles a nd a similar frequency of large deletions, whereas CAA displayed great er toxicity and a larger frequency of deletion mutations, These result s suggest that the majority of mutations induced by VC occur through i ts metabolite, CEO.