Induction of malignant transformation in mouse 10T1/2 cells by low-dose-rate exposure to tritiated water and gamma-rays at two different temperatures, 4 degrees C and 37 degrees C.
Cultured mouse (C3H 10T1/2) cells in contact-inhibited state were subjected to protracted exposure at 4 degrees C or 37 degrees C to either beta-rays from HTO or 60Co gamma-rays. The duration of exposure was 20 h and the total dose was varied by changing the dose-rate. The dose-survival and dose-transformation curves for gamma-irradiation at 4 degrees C were close to those obtained after a single acute X-ray dose (0.5 Gy/min). When gamma-irradiation was administered at 37 degrees C, both the lethality and transformation induction were lower than those after the corresponding doses at 4 degrees C, presumably owing to repair of lethal and transformational damage during gamma-irradiation at 37 degrees C. The same effect of temperature was observed in the case of HTO exposure, indicating again the existence of repair of damage during beta-irradiation at 37 degrees C but not at 4 degrees C. These facts strongly suggest that when irradiated at a low temperature such as 4 degrees C, both the dose-lethality and dose-transformation induction relationships were independent of the dose-rate for either gamma- or beta-exposure, at least the dose-rates used in this experiment. Thus, the comparison of radiation effectiveness between beta- and gamma-exposures at 4 degrees C gave reliable values of relative biological effectiveness (RBE) of tritium beta-rays which were ca. 1.4 at the D0 for lethality and 1.6 for cell transformation within the dose range examined (1 to 6 Gy of beta-rays). The comparison between exposures at 37 degrees C resulted in RBE values (1.4 and 1.7, respectively) very close to those at 4 degrees C.
T
T
Yamaguchi
M
M
Yasukawa
T
T
Terasima
H
H
Matsudaira
D000818:Animals; D001610:Beta Particles; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D002478:Cells, Cultured; D005720:Gamma Rays; D051379:Mice; D011829:Radiation Dosage; D012062:Relative Biological Effectiveness; D013696:Temperature; D014316:Tritium / Q000008:administration & dosage / Q000009:adverse effects*; D014867:Water / Q000008:administration & dosage / Q000009:adverse effects*
D014867:Water; D014316:Tritium; C033961:tritium oxide