Effects of pre-exposure of mouse testis with low-dose 16O 8 ions or 60Co gamma -rays on sperm shape abnormalities, lipid peroxidation and superoxide dismutase (SOD) activity induced by subsequent high-dose irradiation

Purpose: To investigate the effects of pre-exposure of mouse testis with low-doses of 16O 8 ions or 60Co gamma -rays on sperm shape abnormalities, lipid peroxidation and superoxide dismutase (SOD) activity induced by subsequent high-dose irradiation. Materials and methods: Testes of the B6C3F hybrid strain mice 1 were pre-irradiated with 0.05 Gy of 16O 8 ions or 60Co gamma -rays and then after 4 h given a test irradiation with 2 Gy of the same radiation type. SOD activity and thiobarbituric acid reactive substances (TBARS) in the testes were determined by spectrophotometric and TBA methods respectively at 4 h after irradiation. Testis weight, sperm count and sperm morphology were analysed at day 35 after irradiation. Results: Compared with controls, there was a significant increase in SOD activity and a significant decrease in TBARS level of pretreated testes. Testis weight loss, sperm count reduction and sperm abnormalities were significantly lower in the pretreated testes. The bioeffects of a 2 Gy dose of 16O 8 ions relative to 60Co gamma -rays were 1.84 0.28 for testis weight, 1.22 0.25 for sperm count and 1.29 0.10 for sperm abnormalities. Conclusions: These data suggest that pre-exposure of testes with a low dose of heavy ions or gamma -rays renders the organ more resistant to subsequent high-dose irradiation. The increase of SOD activity and the decrease of lipid peroxidation levels induced by lowdose ionizing irradiation may be involved in this resistance. The effects with heavy ion irradiation were greater than with gamma -rays.