Protection by WR1065 and WR151326 against fission-neutron-induced mutations at the HGPRT locus in V79 cells.

The radioprotectors WR1065 and WR151326, each at a concentration of 4 mM, protect against cell killing and mutagenesis at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 Chinese hamster fibroblast cells exposed to fission-spectrum neutrons (mean energy of 0.85 MeV) from the JANUS reactor. Significant protection against neutron-induced cell lethality occurred only when the radioprotectors were present during irradiation; e.g., D0's and n's were 82 Gy, 1.27 for control cells; 97 Gy, 1.51 for WR1065-protected cells; and 120 Gy, 1.00 for WR151326-protected cells, respectively. Mutation induction by JANUS fission-spectrum neutrons was linear over the dose range tested giving rise to a mutation frequency of 109.3 x 10(-6)/Gy. In comparison with 60Co gamma rays (mutation frequency 8.7 X 10(-6)/Gy), JANUS neutrons, at a dose rate of 24 cGy/min, were over 12 times more effective in inducing HGPRT mutations. Both WR1065 and WR151326 afforded protection against the induction of mutants by neutrons, even when they were administered up to 3 h after irradiation; i.e., mutation frequencies were 40.9, 48.8 and 68.6 X 10(-6)/Gy for WR1065 present during, present immediately after, or added 3 h after irradiation, respectively; and 61.7, 47.8, and 68.5 X 10(-6)/Gy for WR151326 present at the same times.