Impaired Renal Afferent Arteriolar Contraction To Angiotensin â…¡ In Mice With Renal Ischemia Reperfusion Injury:Role Of Hydrogen Peroxide

Aim:Renal ischemia reperfusion injury increases renal generation of angiotensin II (Ang II) which could worsen the injury. The current study investigated the hypothesis that renal ischemia reperfusion injury (IRI) alters renal afferent arteriolar responses to Ang II via production of hydrogen peroxide (H2O2), or superoxide (02.-) or via altered angiotensin type 1 receptor (AT1R) expression.Methods:Sixteen male C57B1/6 mice,8～12 weeks, weighing 20～25 g, were randomly divided into control group and renal ischemia reperfusion group (IRI).The mice of IRI group were opened the abdominal cavity, and separated the bilateral renal pedicle which was clipped 45 min.In control group, only open the abdominal cavity, separate the bilateral renal pedicle but no occlusion was performed,the animals were observed for 45 min.Draw blood from inferior vena cava after 24h and measure the level of serum creatinine and blood urea nitrogen. Afferent arterioles of mice kidney 24h after renal IRI or sham procedures were isolated and perfused.Responses to Ang II or norepinephrine (NE) were assessed by measurement of arteriolar luminal diameter. The mRNA expressions of AT1 receptor (AT1R) and AT2 receptor (AT2R) were evaluated by quantificational real-time polymerase chain reaction (RT-qPCR).Test the enzyme activity of SOD and CAT in the arteries using the kits.Results:Afferent arterioles isolated from mice kidney after IRI had impaired contractions to Ang Ⅱ(-4.63±3.06% versus-29.95±1.31% at 10-9 mol/L, P<0.05;-27.07±1.50% versus -41.74±0.60% at 10-7 mol/L, P<0.05) that were normalized by incubation with PEG-catalase, but unaffected by PEG-SOD.However, the responses of afferent arterioles after IRI to NE were unchanged.Compared to the sham group, IRI significantly increased the renal cortical H2O2 (0.123±0.006 versus 0.087±0.003 μmol/mg protein, P<0.001), reduced catalase activity (14.81±3.22 versus 28.49±1.62 units/mg protein, P<0.01)and downregulated AT1R mRNA expression (0.27±0.02 versus 0.95±0.02, P<0.01).Conclusion:Renal cortical H2O2 is increased and CAT activity decreased after IRI. Afferent arteriolar responses, especially to Ang Ⅱ, are impaired in mice after IRI by accumulation of H2O2 and reduced expression of AT1R.