Protective Effect Of RhEPO With Different Dosage And Administration Time On Renal Ischemia-Reperfusion Injury In Rats

Backgroud:In renal transplantation,renal ischemia reperfusion injury leads to delayed graft function,which can increase incidence of acute or chronic rejection.The recombinat human erythropoietin(rhEPO) has been widely used for anemia therapy in clinic.But recent studies show rhEPO has some tissue protection via EPO receptor which in kidney,it has also been found.Some prophase reaserch has proved rhEPO can lighten renal ischemia reperfusion injury.However,which dosage and administration time are suitable,there are still unknown.In this experiment,protective effect of rhEPO with different dosage and administration time was investigated after ischemia-reperfusion injury in rat kidneys.Methods:Right nephrectomy was performed on the male Sprague-Dawley rats(200～220g) and left renal ischemia was induced by clamping left renal pedicle for 45 minutes.After the clamp was released,reperfusion was confirmed visually.The rats were subjected to renal ischemia-reperfusion injury or sham operation.Some of them were treated with rhEPO(1000U/kg, 2000U/kg or 3000U/kg) by injection via inferior vena cava 30min before releasing the clamp,the others were treated with rhEPO(1000U/kg, 2000U/kg or 3000U/kg) by injection through left renal vein at the sanme time with releasing the clamp.The rats were scarificed at 24h and 72h after the reperfusion.Blood sample and left kidney tissue were collected(at 6h,we also collected blood sample).The severity of the renal ischemia-reperfusion injury,and oxidation and antioxidation were assessed by serum creatinine levels,urea nitrogen levels,MDA levels,SOD levels,IL-6 levels and renal histology.Apoptosis of tubular epithelium was observed by TUNEL assay and Caspase-3 levels.Results:In ischemia reperfusion injury control group(IR group), significant difference was observed in serum creatinine level,urea nitrogen levels,MDA levels,SOD levels,IL-6 levels,renal histological damage and number of TUNEL-positive cells compared with sham group.No matter which route of administration,at 6 hours and 24 hours after renal ischemia-reperfusion injury,the serum creatinine level,urea nitrogen levels of rhEPO 3000U/kg group was significantly lower than that of IR group.In rhEPO 1000U/kg and 2000U/kg group,they were also lower than IR group,though not significantly rather than rhEPO 3000U/kg.Also,the rhEPO group had lower IL-6 levels and MDA levels,higher SOD levels.Kidney sections from rhEPO 3000U/kg group showed less histological damage and significantly lower number of TUNEL-positive cells than those of IR group. rhEPO 1000U/kg group and rhEPO 2000U/kg group also reduced the histological damage of the kidneys.At 72 hours after renal ischemia-reperfusion injury,we can find similar results between these groups.On test items in the MDA,SOD,IL-6,Caspase-3,we found that delivery into the renal vein at pre-open vessel is better than delivery at the reperfusion time.Conclusion:This study indicated that in renal ischemia reperfusion injury in rats,rhEPO can attenuate renal ischemia-reperfusion injury in a dose-dependent manner.This protective effect might be mediated by its inhibition of immflamitation,oxidation and tubular epithelium apoptosis,thereby reducing the histological damage.We found that delivery into the renal vein at pre-open vessel is better than delivery at the reperfusion time.In clinical kidney transplantation,it means we should injecte rhEPO into renal artery at pre-open vessel.