The effect of a-tocopheryl hemisuccinate (TS) on lipopolysaccharide (LPS)/interferon-c (IFN)-induced nitric oxide production in rat vascular smooth muscle cells (VSMC) was examined. The LPS/IFN-induced NO production was enhanced by TS but not by the other a-tocopherol (a-T) derivatives a-tocopheryl acetate (TA) and a-tocopheryl nicotinate (TN), or a-T itself. a-T, TA and TN inhibited the enhancement by TS of LPS/IFNinduced NO production. The enhancing effect of TS was observed in the presence of LPS, but not IFN, suggesting that TS participates in the LPS-stimulated signal pathway leading to NO production