Chromosomal aberrations induced by 12C6+ heavy ion irradiation in spermatogonia and spermatocytes of mice

The testes of Kun-Ming strain mice were radiated with different doses of 12C6+ ion or 60Co gamma-ray. Chromosomal aberrations induced in spermatogonia and spermatocytes were analyzed by the air-drying method. The relative biological effectiveness (RBE) of 12C6+ ion was calculated with respect to 60Co gamma-ray for the induction of chromosomal aberrations. The 12C6+ ion and 60Co gamma-ray dose-response relationships for chromosomal aberrations were plotted by linear quadratic models. The results showed that there was an increase in frequency of chromosomal aberrations in all the treated groups compared to controls. The RBE values were 1.67 for aberrations of spermatogonia and 1.66 for aberrations of spermatocytes for a dose of 2.0 Gy. Moreover, a different distribution of the various types of aberrations has been found for 12C6+ ion and 60Co gamma-ray irradiations. The dose-response relationships for 12C6+ ion and 60Co gamma-ray exhibited negative curvature in both spermatogonia and spermatocytes groups: the frequencies of aberrations increased sharply at low doses and exhibited less sharp increases for higher doses, which may be related to an interaction between the chromosomal damage and a block in cell cycle. Our results may provide useful information for the assessment of genetic risks of humans exposed to heavy ions.