There is increasing evidence supporting potential roles of aldosterone in the pathogenesis of vascular injury. The present study aimed to determine the involvement of Rho-kinase in aldosterone-induced vascular smooth muscle cell (VSMC) remodeling. In cultured rat VSMC, the effects of aldosterone on Rho-kinase activity, the reorganization of the cytoskeleton and cellular migration were examined. Aldosterone (1 nmol/L) significantly increased phosphorylation of myosin phosphate target subunit-1 (MYPT1), a marker of Rho-kinase activity, and the amount of GTP-Rho with a peak at 90 min in VSMC. Aldosterone also stimulated VSMC stress fiber formation and migration. These effects of aldosterone were markedly attenuated by pretreatment with eplerenone (10 micromol/L), a selective mineralocorticoid receptor antagonist, or Y27632 (10 micromol/L), a specific Rho-kinase inhibitor. These findings indicate that Rho-kinase is involved in the pathogenesis of aldosterone-induced VSMC remodeling.