To elucidate the mechanism(s) involved in periarterial blood-mediated vasospasm in the rat femoral artery, vascular production of superoxide and related expression of intercellular adhesion molecule-1 (ICAM-1) were assessed with subsequent perivascular mobilization of granulocytes and macrophages. Arterial vasospasm characterized by increased wall thickness and decreased lumen size was observed on the side exposed to blood at 7 to 12 days, and these vascular changes were significantly ameliorated by pretreatment with NADH/NADPH oxidase inhibitor, diphenyleneiodonium (200 microM, locally). Increased mobilization of granulocytes was paralleled with the expression of ICAM-1 in the vessels at 24 hours after periarterial application of blood to the femoral artery, and then both declined. Subsequently, infiltration of macrophage progressively increased at all layers throughout 7 to 12 days. In in vitro study, a large amount of superoxide that was inhibitable by diphenyleneiodonium (20 and 100 microM) was produced at 3 hours upon application of 10% autologous blood to the aortic segments. Furthermore, ICAM-1 expression by autologous blood was well correlated with generation of superoxide anion in the aortic segment (r=0.975, P<0.05). Taken together, it is suggested that NADH/NADPH oxidase-derived superoxide is implicated in periarterial blood-induced vasospasm via increased expression of ICAM-1 with subsequent mobilization of granulocyte/macrophage.