Antioxidant effects of vitamin C in mice following X-irradiation

The influence of supplemental vitamin C on the survival of nucleated bone marrow cells was examined in Swiss Webster mice following whole-body sublethal X irradiation (3.5 Gy). The vitamin protected these cells by a factor of 1.7 when cell count per tibia was taken as the biological end point. However, in studies with lethal whole-body irradiation (9 Gy) and 30 day survival as the end point, supplemental ascorbic acid (AA) had no significant effect on the biological outcome. Based on these studies, it appears that vitamin C is effective in protecting the nucleated cells at lower doses, but not at lethal doses. Studies on the mechanism of radioprotection by vitamin C at sublethal doses were carried out by following the response of endogenous AA and glutathione levels to X irradiation (3.5 Gy) on mice fed with regular as well as vitamin C rich diet. The results suggest that i) a glutathione controlled feedback mechanism regulates the plasma AA levels in mice; ii) the role of vitamin C against radiation damage is not only in the initial stages of radical scavenging but also in cellular redox processes mediated by glutathione.