Changes of superoxide dismutase in cultured rat aortic smooth muscle cells(A7r5) by an incubation of vitamin E

Supplementation of antioxidants such as vitamin E and vitamin C as health p romotion food is popular recently. Epidemiological studies supported the be neficial effect of these antioxidants because oxygen free radicals have bee n linked to the process of diseases and aging. The present study evaluated the effect of alpha-tocopherol (vitamin E) on the changes of superoxide dis mutase (SOD) in cultured rat aortic smooth muscle cells (A7r5) after a shor t-term (2 days) or longterm (7 days) incubation. Incubation of A7r5 cells w ith vitamin E at a concentration of 50 mu mol/l for 2 days caused an increa se of both the activity and mRNA level of SOD. At higher concentrations, su ch as 100 or 200 mu mol/l, vitamin E failed to enhance SOD more effectively . However, after incubation for 7 days, vitamin E caused a decrease in both the activity and mRNA level of SOD in a concentration-dependent manner. Ot herwise, the protein amount of SOD remained the same in these samples regar dless of the concentration of vitamin E or the duration of incubation. The obtained results suggest that vitamin E can increase the effect of SOD to r esult in the beneficial influence of this antioxidant only at low concentra tion under a short-term supplementation because a down-regulation of SOD wa s observed in cells receiving a long-term incubation.