Inter-chromosomal variation in aberration frequencies in human lymphocytes exposed to charged particles of LET between 0.5 and 55 keV/μm

Abstract

Purpose: To investigate the distribution of chromosomal aberrations in chromosomes 2, 8 and 14 induced by charged particles, using the fluorescence in situ hybridisation (FISH) technique.Methods: Irradiation of peripheral blood from six healthy volunteers (four male and two female) was performed at the accelerators of the Joint Institute for Nuclear Research (JINR) in Dubna (Russia). Whole blood samples were irradiated with 2 and 3 Gy of protons (170 MeV/nucleon (n), linear energy transfer (LET) ≈ 0.5 keV/μm), 3.5 Gy of 12C ions (480 MeV/n, LET = 10.6 keV/μm), 3 Gy of 12C ions 500 MeV/n, LET = 12 keV/μm), 4 Gy of 7Li ions (30 MeV/n, LET ≈ 20 keV/μm) and 3 Gy of 11B ions (32 MeV/n, LET ≈ 55 keV/μm). Chromosomal aberrations were analysed in metaphase and prematurely condensed chromosomes (PCC) induced in G2-cells using calyculin A. Chromosomes 2, 8 and 14 were painted in different colours and aberrations scored with the help of an image-analysis system.Results: Chromosome 2 was generally less sensitive than expected on the basis of its DNA content. A higher than expected frequency of exchanges was found in chromosomes 8 and 14. On average, the dicentric frequency in chromosome 2 was higher than the translocation frequency, whereas variable dicentric to translocation ratios were observed in chromosomes 8 and 14. When aberrations in all painted chromosomes were summed up the ratio was close to 1. The frequency of complex aberrations correlated with LET.Conclusion: In lymphocytes of donors studied in this work chromosome 2 appears to be consistently less sensitive to protons and heavy ions than chromosomes 8 and 14. Complex aberrations appear to be a potential marker of radiation quality.