Mutagenic effect of low energy neutrons on human chromosome 11.
OBJECTIVE
The shape of the dose-effect curve for neutrons, i.e. the question as to whether the curve is linear or supralinear in the low-dose region, is still not clear. Therefore, the mutagenic effect of very low doses of low-energy neutrons was determined.


METHODS
Human-hamster hybrid A(L) cells contain human chromosome 11, which expresses the membrane protein CD59. This membrane protein can be detected immunologically and quantified by flow cytometry. The A(L) cells were irradiated with neutrons of 0.565, 2.5 or 14.8 MeV and the results were compared with those after 200 kVp X-rays. Before irradiation, cells spontaneously mutated in the CD59 gene were removed by magnetic cell sorting (MACS).


RESULTS
The relative biological effectiveness (RBE) for CD59 mutation induction was 19.8 (+/-2.7) for 0.565 MeV, 10.2 (+/-1.9) for 2.5 MeV, and 10.2 (+/-1.6) for 14.8 MeV neutrons. Linear mutation responses were obtained with all radiations except for 14.8 MeV neutrons where a supralinear curve may be a better fit. The deletion spectrum of mutated cell clones showed 29 Mbp deletions on average after irradiation with 0.069 Gy of 0.565 MeV neutrons. This scale of deletions is similar to that after 3 Gy 100 kV X-rays (=34 Mbp). For 50% cell survival, the RBE of the neutrons was 11 compared with 200 kV X-rays.


CONCLUSIONS
Neutrons of low energies (0.565 or 2.5 MeV) produce a linear dose-response for mutation in the tested dose range of 0.015-0.15 Gy. The neutron curve of 14.8 MeV can be approximated by a curvilinear or linear function.
Göhde
W
W
Institut für Strahlenbiologie Westfälische Universität Münster Robert-Koch-Strasse 43 D-48149 Münster Germany. greveb@uni-muenster.de
Uthe
D
D
Wedemeyer
N
N
Severin
E
E
Greif
K
K
Schlegel
D
D
Brede
H J
HJ
Köhnlein
W
W
D000818:Animals; D018957:CD59 Antigens / Q000096:biosynthesis; D002469:Cell Separation; D002880:Chromosomes, Human, Pair 11 / Q000528:radiation effects*; D006224:Cricetinae; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D017353:Gene Deletion; D006801:Humans; D006822:Hybrid Cells; D016130:Immunophenotyping; D008280:Magnetics; D016296:Mutagenesis; D009153:Mutagens; D009154:Mutation; D009502:Neutrons; D016133:Polymerase Chain Reaction; D012062:Relative Biological Effectiveness; D014965:X-Rays
D018957:CD59 Antigens; D009153:Mutagens