The objective of this study was to investigate the effects of cadmium on DNA damage of lung cells in immature animals. Seventy-two immature mice were randomly divided into twelve cadmium-ingested groups including low dose (1/100 LD₅₀, 1.87 mg/kg BW), middle dose (1/50 LD₅₀, 3.74 mg/kg BW), high dose (1/25 LD₅₀, 7.48 mg/kg BW) and control group, and exposed to cadmium chloride for 10, 20 and 30 days, respectively. Mice were sacrificed after cadmium exposure for different time, and lung cells were collected to investigate DNA damage by comet assay. The results showed that comet tailing ratio, tail length, comet length, tail moment, Olive tail moment and damaged grade of lung cells from immature mice increased along with increasing of cadmium exposure dose and time. In low dose group treated for 30 days, there was significance (P<0.05) in comet length or high significance (P<0.01) in other parameters compared with control group or low dose group treated for 10 days. When mice were exposed to cadmium at high dose for 30 days, DNA of lung cells was damaged most seriously. Our results indicate that cadmium can induce DNA damage of lung cells from immature mice in dose- dependent and time-dependent manners, and DNA will be damaged when immature mice exposed to cadmium for long time even at low dose. Meanwhile, comet assay can be considered as a powerful and sensitive biomarker assay in risk assessment of immature animals exposed to cadmium.

Key words: Cadmium, Comet assay, DNA damage, Immature mice, Lung cell