| Objective There are many situations which limbs are subjected to ischemic-reperfusion injury(IRI). This pathophysiology course lies in replantation of limb,thrombosis of major blood vessels,transplatation and application of tourniquet. IRI may induce limb disfunction and eventually tissue necrosis. Serious ischemic-reperfusion(I/R) of limb can also cause injury of remote organs. Ischemic preconditioning has been thought to be an best intervention to prevent IRI. In recent years,preconditioning has developed from the classic ischemic preconditioning to pharmacologic preconditioning. Yet studies are focused on heart,liver,brain and kidney,and not enough on limb. In this experiment rat handquarters were subjected 4 hours of ischmia and 2 or 24 hours of reperfusion,four preconditionings include 3 cycles of 5 min or lOmin ischemia and reperfusion,adenosine,diazoxide were performed before ischemia. We observed contratile function,CPK in serum,MDA,NO,MPO in homogenate,no-reflow phenomenon and ultrastructure to understand the early and delayed protective effect.Materials and methods 66 Sprague-Dawley rats randomly divieded into 6 groups:sham operation group,I/R control group,IP 10 group which preconditioning by 3 cycles of 10 minutes ischemia and 10 minutes reperfusion,IPS group pretreated by 3 cycles of 5 minutes ischemia and 5 minutes reperfusion,ADO group by infused adenosine(3.5mg/kg) 10 minutes before,DIA group by infused diazoxide(10mg/kg) 10 minutes before. Anmials' handquarters were subjected 4 hours of ischemia and 2 or 24 hours of reperfusion. At the terminal of reperfusion following item were surveyed.:twitch and tetanus of tibialis anterior muscles,MDA,NO and MPO cotent ofhomogenate,CPK of serum,the no-reflow phenomenon of the tissue section of tibialis anterior muscles under microscope,the ultrastructure of handquarters. Datas were expressed as means + SEM,analysis of variance was used to test for differences on SPSS 10.0,least significant difference test (LSD-t) for multiple comparison.Results 1) IP 10,IPS and ADO preconditioning enhanced the twitch contractility of tibialis anterior muscles at R2h and R24h,IPS and ADO groups were even more effective. DIA preconditioning reduced twitch and tetanus of tibialis anterior muscles at R2h,but improved twitch contractility obviously at R24h. Preconditionings improved the tetanus contractility of tibialis anterior muscles not obviously. Serum CPK of IPS,IP 10 and ADO at R2h and R24h while DIA at only R24h was obviously lower than I/R. 2) Compared with I/R group,DIA,IPS and ADO preconditioning reduced MDA and MPO in homogenate of gastrocnemius. There was no siatistical difference between IP 10 and I/R group. IP 10,IPS,ADO and DIA preconditioning all enhanced NO content of in homogenate of gastrocnemius. IP 10,IPS,and ADQ preconditioning decreased serum CPK markedly at both 2 hours and 24 hours of reperfusion and DIA only at 24h of reperfusion. 3) At 2h of reperfusion the number of functional capillaries which stained by ink of I/R group were significant fewer than sham group and interstitial became wide. Among preconditioning groups,the labeled capillaries were very dense in IPS and ADO group,even higher than sham group. High-power inspection showed that the caliber of capillaries were expanded obviously. Density of Labeling capillaries of DIA and IP 10 group also higher than I/R group. We also found the muscle fibers of DIA group were more swell than other groups. More capillaries were infusioned at 24h of reperfusion than that of 2h of reperfusion in I/R group. Capillaries of IP10,IPS,ADO,DIA were dense at 24h of reperfusion. Compared to R2h,number of infused capillaries were increased in IP 10 group,but reduced in IPS and ADO group. In DIA group,muscle fibers' swell relived to some extent and caliber of capillies increased to some extent. 4) As the result of stereology,the total area ofcapillary of each preconditioning group was obviously larger than that of I/R groups. Under electron microscope,myofibrils rowed unregular,Z lines were not...
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