A 24-h exposure to copper (400 muM, 600 muM) or cadmium (5 muM, 10 muM) significantly reduces the viability of COS-7 cells. A 2-h preincubation with vitamin E does not protect COS-7 cells from copper-induced toxicity, but does protect against cadmium-induced toxicity. Preincubation with aspirin protects cells from both copper- and cadmium-induced toxicity. A combination of aspirin and vitamin E (10 muM and 25 muM, respectively) increases cell viability in copper-exposed cells in a clearly additive manner, while in cadmium-exposed cells the effects are slightly additive. These results indicate that aspirin and vitamin E can protect cells from metal-induced toxicity. Differences in the protective effects of aspirin and vitamin E on copper versus cadmium-induced toxicity may be due to alternative mechanisms of metal toxicity or antioxidant activity.