The purpose of this study was to determine whether expression of inducible nitric oxide synthase (iNOS) is altered in vascular smooth muscle cells of type 2 diabetes rats. We used cultured aortic smooth muscle cells (ASMCs) isolated from male Goto-Kakizaki diabetes rats (G-K rats) aged 27-28weeks and age-matched Wistar rats (control rats). iNOS and extracellular signal-regulated kinase (ERK) were evaluated by immunoblot and/or immunochemical analyses, and NO production was evaluated by measuring NO(X) (NO(2) and NO(3)). Expression of iNOS was not detected in ASMCs of either G-K or control rats under a resting condition. Stimulation with interleukin-1beta (IL-1beta) induced iNOS expression, which was much greater in ASMCs from G-K rats than in ASMCs from control rats. When ASMCs were stimulated with IL-1beta, the number of iNOS-immunoreactive ASMCs from G-K rats increased more prominently than did the number of such ASMCs from control rats. IL-1beta-induced NO production was also much greater in ASMCs from G-K rats than in those from control rats. Both IL-1beta-induced iNOS expression and NO production in ASMCs of G-K and control rats were markedly reduced in the presence of an ERK inhibitor, U0126 or PD98059. Both basal and IL-1beta-stimulated levels of ERK activity were significantly higher in ASMCs from G-K rats than in ASMCs from control rats. The results suggest that iNOS induction is enhanced in cultured ASMCs from G-K rats and that this enhancement is associated with increased ERK activity.