Urinary excretion of mutagens and covalent DNA damage induced in the bladder and kidney after passive smoking in rats

Using 32P-postlabeling assay, we studied the effect of sidestream smoke of cigarettes, so-called passive smoking, on the covalent DNA adduct formation in an animal model. Urine samples of 18 rats, 9 male and 9 female, before smoking resulted in an average of 2.4 adducts per 1×107 nucleotides per 24-h urine of a rat in the target plasmid DNA after incubation for 2 h in vitro. Urine samples of 4 out of 6 rats after exposure to sidestream smoke induced additional adducts in the target DNA. The incidence increased to 17.5 adducts per 1×107 nucleotides per 24-h urine of a rat. Without exposure to smoke, no increase in the adduct formation was observed. Adduct formations similar to those induced in vitro were detected in the bladder and kidney DNA, but not in the testicular DNA, of the four rats exposed to sidestream smoke. These observations suggest that passive smoking causes covalent DNA damage of the cells in the bladder and kidney by excreting chemicals in urine. Passive smoking as well as active smoking might contribute to the bladder and renal carcinogenic process.