Decreased vascular contractility induced by hemin is associated with a reduced rho-kinase activity

OBJECTIVES: In this study, the role of rho-kinase activity in the modulation of vascular contractility induced by hemin, a heme oxygenase inducer, was investigated. METHODS: Aortic rings from Wistar rats were incubated in physiological saline solution (PSS) containing hemin at 10-4 M for six hours then contracted with phenylephrine, and a dose-response curve was established. The effect of Y-27632, a rho-kinase inhibitor, on the relaxation of the pre-contracted aortic rings was then studied. RESULTS: Incubation of the aortic rings in hemin induced an increased expression of heme oxygenase 1 (HO-1). A reduction in the contractile force of aortic rings incubated in hemin was observed in response to phenylephrine. Y-27632 at a concentration of 10-6 M induced a 36% relaxation of the control aortic rings but only a 20% relaxation in aortic rings treated with hemin. CONCLUSION: These data suggest that the decreased vascular contractility induced by hemin could, in part, result from an inhibition of rho-kinase activity.