In Vivo Mutagenesis Caused by Diesel Exhaust in the Testis of gpt delta Transgenic Mice

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Diesel exhaust(DE) is a major airborne pollutant in urban areas. In this study, we estimated the systemic effect of diesel exhaust inhalation by investigating mutations in extraplumonary organs such as the testis and liver. gpt delta Transgenic mice carrying the guanine phosphoribosyltransferase (gpt) transgene for the detection of mutations in genomic DNA were exposed to inhalation of 3mg m^<-3> diesel exhaust (as suspended particulate matter) for 12 or 24 weeks. Compared to the control mice, DE resulted in a 2.0-fold increase in mutant frequency in the testis of mice that were exposed to DE for 24 weeks (inhaled group, 1.17×10^<-5>; control group, 0.57×10^<-5>), but not in the testis of mice exposed for 12 weeks (0.61×10^<-5>). The mutant frequency in the lungs was 2.6-fold higher in mice exposed to DE for 24 weeks than the control group, but it was not elevated in the liver (0.67×10^<-5>). In the testis, the major mutations on the gpt gene were G:C→T:A transversions, 1 base deletions and G:C→A:T transitions, while the major mutation in the lung was G:C→A:T transitions. The mutations on nucleotide nos. 402, 406, 409 and 416-418 in the gpt gene in testis seemed to be characteristic of DE inhalation in the testis. Our results suggest that inhalation of diesel exhaust is genotoxic to the testis as well as respiratory organs.
2009-02-20