[Manifestation of the adaptive response and bystander-effect of C3H10T1/2 fibroblasts irradiated by protons and gamma-rays].

Adaptive response and bystander-effect were studied in mice fibroblasts irradiated by gamma-rays and protons with the energy of 150 MeV Monolayer of fibroblasts cultivated on the wall of a plastic vial first were exposed to 2 and 4 cGy of ionizing radiation (presumably adaptive doses) and later, after 40-min. or 16-hr. period at 37 degrees C, to damaging 4 Gy. To study the bystander-effect, either the whole vial surface (25 cm2) or central area (1 cm2) were irradiated by a beam of protons. The results showed that the preliminary gamma-irradiation 40-min. or 16-hr. before exposure to the damaging dose equally alleviates the harmful effect of protons on fibroblasts. The adaptive response was observed as in the cells subjected to the direct irradiation by protons at 4 Gy, so in bystander-cells. When protons were used for adaptive irradiation, the response was visible only to the dose of 4 cGy in fibroblasts exposed to gamma-radiation 16 hrs. later. In all the rest cases, proton- and gamma-induced damages added together. Besides, the experiments showed that the adaptive effect of protons is passed on to bystander-cells. Adaptive and damaging gamma-irradiation evoked the response invariably.