The Protective Effect Of Ischemic Preconditioning On Rat Muscle Flap Against Ischemic/Reperfusion Injury

Objective: To investigate the protective effects of ischemic preconditioning on rat muscle flap against ischemic/eperfusion injury at different time points of NO and ET levels and the ratio of ET/NO,compared with the regional ischemic preconditioning,and explore the potential protective effect.Methods: Eighty male Sprague-Dawley rats,weighting 250-300 g,were randomly divided into four groups(n=20 per group).Blank control group(Sham group),subjected to the sham operation.Ischemia reperfusion group(IR group),underwent 3h occlusion of the thoracodosal artery followed reperfusion.Regional ischemia preconditioning group(IPC group),underwent 10 min occlusion of the thoracodosal artery.Limb remote ischemic preconditioning group(RIPC group),underwent 10 min occlusion of the right femoral artery.10 min no flow ischemia with 10 min reperfusion three times were used in the ischemic preconditioning.Group IPC and Group RIPC waited for 30 min at the end of ischemic preconditioning,and then to ischemic operations.Each group were randomly divided into two subgroups.The blood samples were harvested in 1 sub group in prior to ischemia(T0),3 h after ischemia(T1),and 1 h afterreperfusion(T2),followed by measurement of the levels of serum NO,ET and ET/NO ratio.5 days after operation,pathological changes of the latissimus dorsi muscle were detected by HE staining.The muscle tissue were harvested in 2 sub group in prior to ischemia(T0),3 h after ischemia(T1),1 h after reperfusion(T2),3 h after reperfusion(T3),and 6 h after reperfusion(T4),followed by measurement of the levels of muscle homogenate NO,ET and ET/NO ratio.Results: Compared with sham group,the content of serum NO were significantly increased,and the content of serum ET and the ratio of ET/NO were significantly decreased in the IPC1 and RIPC1 group at the 3 h after ischemia(T1)and 1 h after reperfusion(T2)(P<0.05),the two groups had no significant difference(P>0.05);compared with IR2 group,the degeneration of myocutaneous flap significantly lessened under microscope at the 5 days after operation in the IPC1 and RIPC1 group,the two groups had no significant difference;compared with IR2 group,the content of muscle homogenate NO were significantly increased,and the content of muscle homogenate ET and the ratio of ET/NO were significantly decreased in the IPC2 and RIPC2 group at the3 h after ischemia(T1),1 h after reperfusion(T2),3 h after reperfusion(T3)and 6h after reperfusion(T4)(P<0.05),but at the 3 h after ischemia(T1),1 h after reperfusion(T2),compared with RIPC2 group,the content of muscle homogenate NO were significantly increased,the content of muscle homogenate ET and the ratio of ET/NO were significantly decreased in IPC2 group(P<0.05),but the two groups had no significant difference at the 3 h after reperfusion(T3),6 h after reperfusion(T4)(P>0.05).Conclusions: Limb remote ischemic preconditioning has a good protection on rat myocutaneous flap against ischemia reperfusion injury the same as regional ischemic preconditioning.The mechanism of the protectionmay be related to increase of contents of NO,decrease of contents of ET,regulate of balance of ET/NO ratio and maintain of stability of Vascular endothelial cell function.