RESUMO
Much evidence gathered in the last years involve the free radicals (FR) in the mechanisms of initiation, development of neoplastic transformations in vivo and in vitro, as well as in the activity of specific oncogenes. Most of it comes from the fact that the agents that remove the FR or interfere in the chain of events induced by FR can inhibit the neoplastic process both at cellular and molecular level. The antioxidant and free-radical scavenging activities of vitamin C have been intensely investigated, vitamin C being considered the most important antioxidant protective agent in the plasma. Our study is focused on the changes in lipid peroxides (MDA), free SH groups and the total antioxidative capacity in the plasma of 22 patients with differentiated thyroid cancer operated and treated with 131I, and then given 1 g vitamin C/day along one month. Blood samples were collected before 131I and then 4 days following 131I administration, and after 1 month of vitamin C administration per os. The following results were noted: (1) an increase of MDA concentration after 131I; (2) a decrease in the MDA level after one month of vitamin C administration; (3) an increase in the concentration of free SH groups after 131I; (4) a decrease in the level of free SH after vitamin C, and (5) a non-significant decrease in TAC after 131I and vitamin C. The results confirm the change in the balance between the oxidative and antioxidative factors under the effect of ionizing radiations and suggest the involvement of vitamin C as a protective and/or potentiating factor for the other antioxidative systems.
