Mutation induction by very low dose rate gamma rays in cultured mouse leukemia cells L5178Y.
Induction of cell killing and mutation to 6-thioguanine resistance was studied in growing mouse leukemia cells in culture following gamma rays at dose rates of 30 Gy/h, 20 cGy/h, and 6.3 mGy/h, i.e., acute, low dose rate, and very low dose rate irradiation. A marked increase was observed in the cell survival with decreasing dose rate; no reduction in the surviving fraction was detected after irradiation at 6.3 mGy/h until a total dose of 4 Gy. Similarly, the induced mutation frequency decreased after low dose rate irradiation compared to acute irradiation. However, the frequency after irradiation at 6.3 mGy/h was unexpectedly high and remained at a level which was intermediate between acute and low dose rate irradiation. No appreciable changes were observed in the responses to acute gamma rays (in terms of cell killing and mutation induction) in the cells which had experienced very low dose rate irradiation.
Furuno-Fukushi
I
I
Division of Biology, National Institute of Radiological Sciences, Chiba-shi, Japan.
Ueno
A M
AM
Matsudaira
H
H
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004351:Drug Resistance / Q000235:genetics; D005720:Gamma Rays / Q000009:adverse effects; D007940:Leukemia L5178 / Q000235:genetics; D051379:Mice; D009154:Mutation; D011831:Radiation Genetics; D013866:Thioguanine / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000528:radiation effects
D013866:Thioguanine