In the present study, the total antioxidant status was used as a biomarker to evaluate oxidative stress induced by proton, HZE-particle and gamma radiation in CBA mice. The results demonstrated that the plasma level of TAS was significantly decreased (P < 0.05) in CBA mice after exposure to a 50-cGy dose of radiation from HZE particles or a 3-Gy dose of radiation from protons or gamma rays. Diet supplementation with Bowman-Birk Inhibitor Concentrate (BBIC), L-selenomethionine (L-SeM), or a combination of N-acetyl cysteine, sodium ascorbate, co-enzyme Q10 (CoQ10), alpha-lipoic acid, L-SeM and vitamin E succinate could partially or completely prevent the reduction in the plasma level of TAS in CBA mice exposed to proton or HZE-particle radiation. The selected antioxidant combination with or without CoQ10 has a comparable protective effect on the gamma-radiation-induced drop in TAS in CBA mice. These results indicate that BBIC, L-SeM and the selected antioxidant combinations may serve as countermeasures for space radiation-induced adverse biological effects.

Rapidly growing Swiss 3T3 fibroblasts possess a bumetanide-sensitive K+ transport system that is dependent on both Na+ and Cl- ions; a smaller bumetanide-insensitive component of K+ transport is also present. In cells brought to the quiescent state by 8-11 days of incubation without a medium change, the bumetanide-sensitive rate of transport was reduced by 63%; the bumetanide-insensitive rate did not change. Removal of dialyzed fetal calf serum from the uptake medium resulted in a substantial reduction in bumetanide-sensitive uptake in both rapidly growing cells (33% reduction) and quiescent cells (68% reduction) but had no effect on bumetanide-insensitive uptake. Insulin was almost as effective as dialyzed fetal calf serum in stimulating bumetanide-sensitive uptake; insulin was maximally stimulatory at 2.5 micrograms/ml. The combination of insulin, epidermal growth factor, and arginine-vasopressin was maximally effective in stimulating both bumetanide-sensitive K+ uptake and 3H-thymidine incorporation in quiescent cells; bumetanide, however, did not interfere with the hormonal stimulation of DNA synthesis. Thus, the bumetanide-sensitive K+ transport system is not necessary for such stimulation to occur. Furthermore, concentrations of hormones which stimulated significant levels of DNA synthesis produced no elevation in the intracellular concentration of K+. We conclude that the bumetanide-sensitive pathway of K+ transport is modulated by serum and by mitogenic hormones, but does not play a role in the stimulation of DNA synthesis by these factors.

No abstract

Of particular concern for the health of astronauts during space travel is radiation from protons and high-mass, high-atomic-number (Z), and high-energy particles (HZE particles). Space radiation is known to induce oxidative stress in astronauts after extended space flight. In the present study, the total antioxidant status was used as a biomarker to evaluate oxidative stress induced by gamma rays, protons and HZE-particle radiation. The results demonstrate that the plasma level of total antioxidants in Sprague-Dawley rats was significantly decreased (P < 0.01) in a dose-dependent manner within 4 h after exposure to gamma rays. Exposure to protons and HZE-particle radiation also significantly decreased the serum or plasma level of total antioxidants in the irradiated animals. Diet supplementation with L-selenomethionine alone or a combination of selected antioxidant agents was shown to partially or completely prevent the decrease in the serum or plasma levels of total antioxidants in animals exposed to gamma rays, protons or HZE particles. These findings suggest that exposure to space radiation may compromise the capacity of the host antioxidant defense and that this adverse biological effect can be prevented at least partially by dietary supplementation with L-selenomethionine and antioxidants.

This study was undertaken to evaluate the protective effects of the soybean-derived Bowman-Birk inhibitor (BBI), BBI concentrate (BBIC) and/or antioxidants against the adverse biological effects induced by space radiation in cultured human epithelial cells. The effects of BBI, BBIC and a combination of ascorbic acid, co-enzyme Q10, L-selenomethionine (SeM) and vitamin E succinate on proton and HZE-particle [high-energy (high E) nuclei of heavier (high atomic number, Z) elements] radiation-induced cytotoxicity in MCF10 human breast epithelial cells and a phenotypic change associated with transformation in HTori-3 human thyroid epithelial cells were assessed with a clonogenic survival assay and a soft agar colony formation assay. The results demonstrate that BBIC and antioxidants are effective in protecting against space radiation-induced cytotoxicity in MCF10 cells and BBI, BBIC and antioxidants are effective in protecting against a space radiation-induced phenotypic change associated with transformation of HTori-3 cells.