Do OH radicals react with organic substances in gamma-irradiated frozen cells of golden hamster embryo?

Reactivity of OH radicals, produced by γ-irradiation, in golden hamster embryo (GHE) cells and in phosphate-buffered saline (PBS) solutions containing nuclei of the GHE cells was studied at 77 and 111 K by ESR spectroscopy. Since OH radicals do not diffuse in frozen cells at 77 K, they do not react with organic substances, such as protein and DNA, in the cells at 77 K. The efficiency of production and trapping of OH radicals at high concentration of organic substances in cells are the same as that at low concentration. Thus OH radicals produced near the organic substances do not react with them, being trapped at 77 K. When GHE cells or PBS-nuclei solutions are irradiated by γ-rays at 77 K and then warmed to 111 K, OH radicals decay fast, while the amounts of organic radicals remain constant at this temperature. These results indicate that OH radicals do not react with organic substances in γ-irradiated cells during warming of the irradiated cells. Therefore it was concluded that OH radicals are not the main reactive species responsible for biological effects in γ-irradiated frozen cells.