To estimate reproductive risks of heavy ion irradiation and the possible mechanism

Kunming strain mice abdomen were exposed to 0

0.5

1

2 or 3 Gy of 12C6+ ions.The DNA content

percentage of each cell-cycle phase and the apoptosis rate were obtained with flow cytometry method.Lipid peroxidation indices

such as malondialdehyde(MDA) level and antioxidants

represented with superoxide dismutase(SOD) activity in the testes were determined by chemical reagent kids.The results showed that SOD activity enhanced slightly in the 0.5 Gy irradiation group(P>0.05)

but decreased with increasing doses

and significant fall was observed in 2 and 3 Gy on groups comparing with the control(P<0.05).The MDA levels increased with the dose

and significant difference was found in the 2 and 3 Gy groups(P<0.05).The flow cytometry data showed that 1～3 Gy of 12C6+ ion irradiation resulted in significant decrease in haploid

diploid and tetraploid cells(p<0.01) and evidently increased apoptosis rate(p<0.01) in testes tissue.The G2/M phase arrest in irradiation groups were extremely obvious(p<0.01).The data suggest that 12C6+ ion irradiation can lead to testes cell high apoptosis rate and cell cycle alteration

which is possibly mediated through oxidative damage induced by over free radicals.The study may provide theoretical basis for application of antioxidants or radical scavengers on protecting gonads from damages during clinical radiotherapy.