Protection of mice against X-ray injuries by the post-irradiation administration of guanosine and inosine

To examine the radioprotective action of guanosine (Guo) and inosine (Ino) administered to mice after irradiation with X-rays.Survival of mice exposed to lethal and sublethal doses of X-rays was studied. Peripheral blood cells were counted using a light microscope. The damage to bone marrow cells was assessed by micronucleus (MN) test. Damage and repair of DNA in blood leukocytes were estimated using the comet assay.Mice injected intraperitoneally (i.p.) with Guo or Ino ( approximately 30 microg g(-1), i.e., approximately 0.6 mg per 20-g mouse) 15 min after acute whole-body irradiation with 7 Gy recovered from X-ray injury. On the 30th day after irradiation, 50 and 40% of mice injected with Guo and Ino, respectively, remained alive. The dose reduction factor (DRF) was 1.23 for Guo and 1.15 for Ino. The protective effect gradually decreased as the time interval between the irradiation and injection was increased to 3, 5, 8 h. Guo and Ino facilitated the restoration of peripheral blood cell counts. These compounds protected bone marrow cells from damage and normalized erythropoiesis. Guo and Ino contributed to a more rapid and complete repair of DNA in mouse leukocytes irradiated both in vitro and in vivo.Guo and Ino introduced shortly after irradiation reduce leukopenia and thrombocytopenia and offer promise as therapeutic agents for treatment of radiation injuries.