Effects Of Ischemic Postconditioning On Oxygen Free Radical Of The Renal Ischemia Reperfusion In Rats

Ischemia reperfusion injury (IRI) is the phenomenon in which the injury of the tissues and the organs getting more and more serious after being reperfused on the basic of ischemia. It is generally accepted that IRI is a process from a reversible injury—ischemia injury to an inreversible injury—reperfusion injury. The pathogenesis of ischemia reperfusion injury involves calcium overload, generation of oxygen free radicals, the activation of the apoptosis gene and the disorder of mitochondria function. Oxygen free radicals are considered to be one of important factors involved in the pathophysiology of ischemia-reperfusion injury. Ischemic postconditioning (IPO) is a new pattern against ischemia reperfusion injury of the tissues and the organs, which is defined as a series of brief interruptions between prereperfusions applied before whole regain of reperfusion. Recent studies revealed that IPO may protect the heart, brain, liver and kidney against ischemia reperfusion injury. However, the mechanism of protection need to further research. Ligustrazine have powerful antioxidation during protect tissues and the organs against IRI, and its protection has been reported. So in our experiment, we established rat model of ischemic postconditioning. Then we researched the effects of ischemic postconditioning on oxygen free radical at different time of the renal ischemia reperfusion in rats, and compare the effect with Ligustrazine based on the rat model of ischemic postconditioning. In this way, we tried to find the possible mechanisms of the ischemic postconditioning protect the kidney against ischemia reperfusion injury.Objective: To establish rat model of ischemic postconditioning, and investigate the effects of ischemic postconditioning on oxygen free radical at different time during renal ischemia reperfusion by the rat model. To compare the protective effect between ischemic postconditioning and Ligustrazine. To discuss the possible mechanisms of the ischemic postconditioning inhibited the production of oxygen free radicals.Methods: 1 To establish rat model of ischemic postconditioning: right renal pedicle of rat was ligated and left arteria renalis was clamped for 45 min. Then the left arteria renalis was underwent 10 cycles of reperfusion-ischemia with the duration of 20s after 45 min kidney ischemia.2 Seventy-two female SD rats were randomly divided into 3 groups (n=24, each group), include sham operation group(S group), ischemia reperfusion group (I/R group) and ischemic postconditioning group(IPO group). Every group was further subdivided into eight groups(0.5 h, 1 h, 3 h, 6 h, 12 h, 24 h, 48 h and 72 h groups). The blood samples and the nephridial tissues were taken from rats of the every groups. The serum urea nitrogen(BUN)and creatinine (Cr) levels were measured to assess the function of the kidney, the renal superoxide dismutase (SOD) activities, catalase ( CAT ) activities, malondialdehyde(MDA)contents and total anti-oxidant capacity (TAC) were detected to assess oxidative damages of the kidney tissue.3 Thirty-two female SD rats were randomly divided into 4 groups (n=8 each), include sham operation group(S group), ischemia reperfusion group (I/R group), Ligustrazine treatment group(I/R+T group), ischemic postconditioning group(IPO group). The blood samples were draw from the inferior vena and the nephridial tissues were homogenated after 24 h reperfusion. The serum urea nitrogen(BUN)and creatinine (Cr) levels were measured to assess the function of the kidney, the renal superoxide dismutase (SOD) activities, catalase (CAT) activities, malondialdehyde (MDA) contents and total anti-oxidant capacity (TAC) were detected to assess oxidative damages of the kidney tissue.Results: Compared with the I/R group, the levels of BUN in IPO group after reperfusion 6 h(10.69±4.16 vs 18.51±1.60 mmol/L),12 h(15.77±0.91 vs 24.69±7.46 mmol/L)and 24 h(8.02±0.61 vs 30.97±9.96 mmol/L)were significantly lower(P<0.05),and the levels of Cr in IPO group after reperfusion 6 h(51.6±24.6 vs 93.3±21.3μmol/L),12 h(44.6±3.5 vs 142.3±66.6μmol/L)and 24 h(44.0±4.5 vs 238.3±54.2μmol/L)were significantly lower(P<0.05).Compared with the I/R group, the levels of SOD, CAT and TAC in IPO group were significantly higher(P<0.05), while the level of MDA was significantly lowe(rP<0.05)at the 3 h, 6 h, 12 h and 24 h after reperfusion , with the level of SOD respectively(90.13±5.17 vs 82.65±0.92 U/mgprot) at the 3 h , (89.34±2.80 vs 79.61±0.76 U/mgprot)at the 6 h ,(92.78±2.47 vs 73.81±0.85 U/mgprot) at the 12 h and(90.21±1.83 vs 72.29±3.28 U/mgprot)at the 24 h , and the level of CAT respectively(21.67±0.94 vs 20.09±0.26 U/mgprot), (21.63±1.10 vs 19.31±1.00 U/mgprot)(,20.57±1.04 vs 18.12±0.37 U/mgprot) and(19.64±0.52 vs 17.79±0.22 U/mgprot)at the 3 h , 6 h ,12 h and 24 h, and the level of TAC respectively(4.05±0.13 vs 3.54±0.10 U/mgprot),(3.87±0.14 vs 3.43±0.08 U/mgprot)(,3.78±0.14 vs 3.22±0.04 U/mgpro), and (3.67±0.23 vs 3.17±0.17 U/mgprot)at the 3 h , 6 h ,12 h and 24 h, and the level of MDA (7.92±0.76 vs 9.21±0.61 nmol/mgprot), (8.66±0.48 vs 10.53±0.96 nmol/mgprot), (8.66±0.48vs 10.53±0.96 nmol/mgprot), (8.96±0.21 vs 10.71±0.13 nmol/mgprot) at the 3 h , 6 h ,12 h and 24 h after reperfusion. Compared with the I/R group, the levels of GSH-Px in IPO group at the 1 h(99.77±1.64 vs 96.60±1.09 U/mgprot),3 h(92.22±5.32 vs 84.44±1.22 U/mgprot),6 h(87.80±6.50 vs 77.83±2.27 U/mgprot)and 12 h(97.76±4.91 vs 86.67±1.07 U/mgprot)after reperfusion were significantly higher(P<0.05).The levels of BUN, Cr, SOD, MDA, CAT and TAC were no significant difference(P>0.05)between Ligustrazine treatment group and IPO group at 24 h after reperfusion.Conclusion: The renal oxidative damages of rats were more and more serious after being reperfused, and the peak was at the 24 h after reperfusion. Ischemic postconditioning may protect the kidney from ischemia reperfusion injury in rats by inhibiting the production of free radicals during the time of 3-24 h after reperfusion, and the inhibition were obviously at the 12 h,24 h after reperfusion. There was no significant difference in protective effect between Ligustrazine treatment group and IPO group at 24 h after reperfusion.