RESUMO
Objective To explore the role of hydrogen peroxide in mesenteric artery contraction of cirrhotic rats with portal hypertension,which was induced by bile duct ligation.Possible mechanism in RhoA/ROCK signal pathway was also part of the focus.Methods The bile duct ligation-induced cirrhotic rats and normal rats (control group) were treated equally with PEG-catalase(10 000 U/kg-1 · d-1,ip.) or by its vehicle for 8 days.Then the level of H2O2 in mesenteric arteries was detected.The contractile response to norepinephrine of arterioles was analyzed by vascular perfusion system.The protein expressions of the α1 adrenergic receptor,β-arrestin-2 and Rho kinase-1 (ROCK-1),and the activity of ROCK-1 were measured by western blot.In addition,the interaction of α1-adrenergic receptor with β-arrestin-2 was assessed by co-immunoprecipitation.Results Compared to normal rats,the dose-response curve of the mesenteric arterioles in response to norepinephrine shifted to the right,and the EC 50 increased in the rats with portal hypertension.PEG-catalase treatment can decrease the hydrogen peroxide level in arteries,thus significantly lowered EC50 and improved the reactivity to norepinephrine of the mesenteric arterioles in portal hypertension rats.No significant difference in the α1-adrenergic receptor amounts was observed among groups.There was remarkable decreases in the protein expressions of β-arrestin-2 and its interaction with the α1-adrenergic receptor in cirrhotic rats with PEG-catalase treatment.PEG-catalase also increased the amount and activity of ROCK-1 in cirrhotic rats.Conclusions The level of hydrogen peroxide increases in the mesenteric arteries in bile duct ligation-induced cirrhotic rats.And it enhances the β-arrestin-2 expression and its interaction with the α1-adrenergic receptor,which subsequently decreases the amount and activity of ROCK as well as the contractility of mesenteric arteries in response to vasoconstrictors.