The prevention of X-ray death by selenium salts given after irradiation

Radioprotection by metals: selenium

The need exists for compounds that will protect individuals from high-dose acute radiation exposure in space and the agents that might be less protective but less toxic and longer acting. Metals and metal derivatives provide a small degree of radioprotection (dose reduction factor < or = 1.2 for animal survival after whole-body irradiation). Emphasis is placed here on the radioprotective potential of selenium (Se). Both the inorganic salt, sodium selenite, and the organic Se compound, selenomethionine, enhance the survival of irradiated mice (60Co, 0.2 Gy/min) when injected IP either before (-24 hr and -1 hr) or shortly after (+15 min) radiation exposure. When administered at equitoxic doses (one-fourth LD10; selenomethionine = 4.0 mg/kg Se, sodium selenite = 0.8 mg/kg Se), both drugs enhanced the 30-day survival of mice irradiated at 9 Gy. Survival after 10-Gy exposure was significantly increased only after selenomethionine treatment. An advantage of selenomethionine is lower lethal and behavioral toxicity (locomotor activity depression) compared to sodium selenite, when they are administered at equivalent doses of Se. Sodium selenite administered in combination with WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, enhances the radioprotective effect and reduces the lethal toxicity, but not the behavioral toxicity, of WR-2721. Other studies on radioprotection and protection against chemical carcinogens by different forms of Se are reviewed. As additional animal data and results from human chemoprevention trials become available, consideration also can be given to prolonged administration of Se compounds for protection against long-term radiation effects in space.

Effects of dietary supplementation with selenomethionine on the teratogenic effect of ionizing radiation in mice

Female C3H mice were fed a standard pellet diet (containing 0.2 ppm Se and 30 ppm vit. E) or the same diet supplemented with 0.8 ppm (low dose) or 3.4 ppm (high dose) of selenomethionine for 10 weeks. After mating with males receiving the standard diet the mice were subjected, on the 9th day of pregnancy, to whole body roentgen irradiation of 1.75 Gy. On day 18 of gestation the frequency of resorptions, mortality and the incidence of fetal malformations were studied. Supplementation with Se-methionine resulted in a significant but dose-independent decrease (p less than 0.005) of the number of malformed fetuses from 62 per cent in the irradiated controls to 47 per cent in the low Se-group and high Se-group, respectively. In addition, the number of total malformations as well as fetal resorptions were significantly decreased in a dose-independent manner in the supplemented groups. The decrease in fetal malformations occurred proportionally for all the major malformations observed, i.e. short or kinked tail, rib and vertebral malformations, coloboma and deformation of retina and iris. Glutathione peroxidase activity in whole blood of Se-methionine fed mice was significantly increased. Thus, Se-rich diet may result in scavenaging of radiation-induced hydroperoxides.

Protective effect of selenium against ionizing radiation-induced malformations in mice

A single dose of sodium selenite (0.5 mg Se/kg b.w.) was injected intraperitoneally into mice on day 9 of pregnancy, either 30 min or 2 h before 1.75 Gy whole body irradiation. Administration of selenite 2 h but not 30 min before irradiation resulted in a significant decrease in the number of malformed foetuses (p less than 0.005). The decrease in foetal malformations occurred proportionally for all the major malformations observed, i.e. short or kinked tail, rib and vertebral malformations, coloboma and deformation of retina and iris. In addition, selenium pretreatment also protected against radiation-induced retardation of the sternum of the foetus.