Role of epididymal inflammation in the induction of dominant lethal mutations in Fischer 344 rat sperm by methyl chloride.

This study assessed the possible relationship between methyl chloride (MeCl)-induced epididymal inflammation and the formation of dominant lethal mutations in sperm of Fischer 344 rats. Groups of 40 males were exposed to MeCl (3000 ppm 6 hr/day for 5 days), with or without concurrent treatment with the anti-inflammatory agent 3-amino-1-[m-(trifluoromethyl)phenyl]-2-pyrazoline (BW 755C; 10 mg/kg, i.p. 1 hr pre- and postexposure); BW 755C was shown previously to inhibit MeCl-induced epididymal inflammation. Control groups (n = 20) were either untreated, injected as described above with BW 755C, or injected on the afternoon of day 5 with triethylenemelamine (0.2 mg/kg), a known dominant lethal mutagen. Each male was caged with one female weekly for 3 weeks; 12-18 days after mating, females were killed to assess dominant lethal parameters. In females bred to MeCl-exposed males, significant increases were observed in postimplantation loss at postexposure week 1 (0.84 dead implants per female vs. 0.29 in untreated controls) and in dead implants/total implants at both week 1 (0.10 vs. 0.04 control) and week 2 (0.24 vs. 0.06 control). These increases were not observed in females bred to males treated with BW 755C during MeCl exposure. Coadministration of BW 755C to males along with MeCl also reduced the percentage of mated females with two or more postimplantation losses from 31% to 8% (week 1) and 30% to 12% (week 2). Therefore, the dominant lethal mutations induced by MeCl appear to be a consequence of its induction of inflammation in the epididymis. These data demonstrate the potential genotoxicity of inflammatory processes in vivo.