There are many works dealing with protective effect of glutathione against Xray radiation, but most of them are used subcutaneous or intraperintoneal injection of glutathione to a single large dose of X-ray irradiation. It is reportet by various investigators that the dosage
required to yield the protective effect to X-ray irradiation is about 10 mg ～ 25mg/mouse. In a point of view that glutathione is generally used intravenously in clinics, the author has verified that such an injection given just before the X-irradiation proves to be most effective, As for the minimal optimal dosage of glutathione to yield its protecthive effect it has been found to be 100 mg/kg or 2.5 mg/mouse in average in my experiment. From the survival rate of animals tested, changes in their body weight and changes in the blood picture of rabbits, it has been proven that a considerably smaller dosage of glutathione injected intravenously is effective as compared with generally given subcutaneously or intraperitoneally. It is noteworthy that, whereas there can be observed no significant difference in the protective
effect between the test groups and the control group (X-ray irradiation only), when glutathione injected to whole body irradiated rabbits just before a single large dose, a considerable protective effect could be obtained in the doses of 100 mg/kg injected into the aural vein for consecutive days just before 100 R/day irradiation. This has been verified by the changes observed in the numbers of lymphocytes, leukecytes as well as erythrocytes. It has been also demonstrated that, while a single dose of 100 mg/kg glutathione injected intravenously just before a single large dose of 1,000 R does not show any protective effect, the same dose of glutathions injected intravenously once a day consecutively just before X-irradiation of 100 R/day yields a considerable protecthive effect. In above mention, I think that there are some clinical significans.