ANTIOXIDANT EFFECTS OF VITAMIN-C IN MICE FOLLOWING X-IRRADIATION

The influence of supplemental vitamin C on the survival of nucleated b one marrow cells was examined in Swiss Webster mice following whole-bo dy 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 biologi cal end point. However, in studies with lethal whole-body irradiation (9 Gy) and 30 day survival as the end point, supplemental ascorbic aci d (AA) had no significant effect on the biological outcome. Based on t hese studies, it appears that vitamin C is effective in protecting the nucleated cells at lower doses, but not at lethal doses. Studies on t he mechanism of radioprotection by vitamin C at sublethal doses were c arried 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 v itamin C rich diet. The results suggest that i) a glutathione controll ed 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 medi ated by glutathione.