Mutagenic effects at HPRT locus induced in Chinese hamster ovary cells by thermal neutrons with or without boron compound.

CHO cells were exposed to thermal neutrons and their mutation frequency was determined. The Kyoto University Research Reactor (KUR), which has a very low level of contamination by gamma-rays and fast neutrons was used as a thermal neutron source. Cells were irradiated in the presence or absence of boric acid to determine mutation frequency and cell survival. Thermal neutron irradiation was 2.5 times as mutagenic as gamma-irradiation without boron. In the presence of boron, however, thermal neutron irradiation was from 4.2 to 4.5 times as mutagenic as gamma-irradiation. When the mutation frequency was plotted against the survival fraction, a higher degree of mutagenicity was observed in the presence than in the absence of boron. These results suggest that the enhancement of thermal neutron-induced mutation with boron is strongly associated with alpha-particles released by 10B(n, alpha)7 Li reaction.