[Effect of heme oxygenase-1 on hydrogen peroxide induced hypo-responses in vascular contraction]

To examine the effect of HO-1 inducer hemin on hydrogen peroxide (H2O2) caused decrease in contraction of isolated rat aortic rings, and to elucidate the underlying mechanism.

The thoracic aortic rings with endothelium of male Sprague-Dawley rats were mounted on a bath system. Isometric contractions of aortic rings were measured.

(1) After intraperitoneal injection of HO-1 inducer hemin, HO-1 activity of thoracic aorta and COHb concentration in rat blood enhanced. And it also prevented the decrease in contraction responses to PE which pretreatment of arteries with 300 micromol/L H2O2. (2) Pretreatment of ATP-sensitive potassium channel inhibitor glibenclamide, but not GC inhibitor methylene blue, could partly abolish the protection of hemin in arteries with H2O2 exposure. (3) Hemin could not influence the shift of concentration-response curve to [Ca2+]o in arteries with H2O2 exposure. (4) In Ca(2+) -free K-H solution, exposure of H2O2 reduced caffeine and PE-induced constriction in the rat aortic rings. After pretreatment of hemin, could prevent the decrease in contraction responses to caffeine and PE.

Increase in HO-1 activity could prevent the H2O2 induced decrease in contraction responses to PE in intact aortic rings. The mechanism might be involved in activation of ATP-sensitive potassium channel and mobilization of intracellular calcium stores, but had no relationship with the GC pathway.