| Objective: In this article, a model of renal ischemia -reperfusion injury in rats was established. To study the effects and mechanisms of different dose of remifentanil on renal ischemia-reperfusion injury by observing the structure of renal tissue, renal function and determing the changes of Superoxidedismutase (SOD) , malondialdehyde (MDA), and Ca2+-ATP, in order to offer reference in choosing suitable drugs in operating , anesthesia and analgesic on patients in renal ischemia-reperfusion injury in clinic.Methods: Sixty male Sprague-Dawley (SD) rats were randomly divided into five groups of twelve rats each: control group (S), model group (M), low concentration of remifentanil group (RL), middle concentration of remifentanil group (RM), high concentration of remifentanil group (RH). M group was the model of the renal ischemia-reperfusion injury in rats and it was reproduced according to Basile's method. The rat was anesthesized successfully and then fixed. The caudal vein was cathetered for infusion after heparinization (5U/ml). The rat was operated on abdomen with median incision to expose the kidneys, and the renal artery was isolated. The bilateral renal vessels were occluded for 45 min with vascular clamps, then vascular clamps were removed for reperfusion. If the color of kidney was from dark purple to red, the model of renal ischemia-reperfusion injury was successful. If the color of kidney did not change to the normal red after 5 min, then it was out testing. The rat should be warmed by physical methods during the experiment process. The abdominal incision should suture layer by layer at the end of experiment. The rats in group S were only exposed the bilateral renal artery but not clipped. The rats in group RL, RM, RH were not only received the operations mentioned above, but also infused respectively remifentanil with the speed of 0.2μg·kg-1·min-1, 0.6μg·kg-1·min-1, 1.0μg·kg-1·min-1 , from 15mins before ischemia to 30mins after reperfusion via the caudal vein. The same volume of saline was injected in group S and M. At the time 30 min and 24h after reperfusion, 1 ml blood of each rat was taken out, then centrifuged. Blood urea nitrogen and Serum creatinine were determined by using semi-automatic biochemical analyzer. All rats were killed at 24 hours after reperfusion. The renal tissue samples were obtained. The tissue homogenate were prepared according to the requirements of the measuring biochemical indicators. The content of tissue protein was measured by the method of Coomassie brilliant blue. The content of MDA was measured by the method of thiobarbituric. The activity of SOD was measured by the method of xanthine oxidase. The activity of Ca2+-ATP was measured by the method of inorganic phosphorus color-photoelectric colorimetric. The above-mentioned indicators were measured by tissue protein content of calibration. The contents of blood urea nitrogen (BUN) and serum creatinine (Scr) were determined by the semi-automatic biochemical analyzer. Pathologic changes of renal tissue were observed by Light microscope and the ultrastructural changes of renal tissue were observed by transmission electron microscope.Results: 60 rats were involved in the result analysis:1. The naked eye observation: In group S, the color of renal cortex was incarnadine, and the color of renal medulla was lighter than that in cortex; In group M, the color of renal cortex was pale, and the color of renal medulla was dark red; In group RH, the appearance of renal was close to that in group S; The pathological changes in group RM and RL were more alleviative than those in group M.2. Under the light microscope: In group S, the renal glomeruli was not wizened. The renal tubular epithelial cell was not swollen. The lumen of renal tubulars were not narrow. Renal interstitium was not edema, hyperemia and inflammatory cells infiltration; In group M, the renal glomeruli was wizened. The renal tubular epithelial cells were vacuolar degeneration, necrosis. There were cell debris and tube-type in the lumen of renal tubular. Renal interstitium was with edema, hyperemia and infiltration of many inflammatory cells; In group RH, the renal glomeruli was not wizened. The renal tubular epithelial cells were lightly swollen. The lumen of renal tubulars were not narrow. There were few of inflammatory cell infiltration; In group RL, the renal glomeruli was wizened. The renal tubular epithelial cells were severely swollen. The lumen of renal tubulars were narrow. There were many inflammatory cell infiltration; In group RM, the pathological changes were between those in group RL and group RH.3. Under the transmission electron microscope: In group S, the nucleus of the renal tubular was integrity. There was a large number of mitochondria with no swollen, no vacuolar degeneration and no fracture; In group M, the nucleus of the renal tubular were severely deformed. The mitochondrial were distorted, swollen and broken; In group RH, the nucleus of the renal tubular was basically integrity. The mitochondrial cristae were expanded; In group RL , the nucleus of the renal tubular was basically integrity. Most of the mitochondrial were swollen, fractured and with the disappearance of mitochondrial cristae; In group RM, the ultrastructural changes were between those in group RL and group RH.4. BUN and Scr content: The contents of BUN and Scr in other four groups were higher than those in group S (P<0.01). The contents of BUN and Scr in group RL, RM, RH were lower than those in group M (P<0.01). The contents of BUN and Scr in group RL were lower than those in group RM, RH (P<0.01). The contents of BUN and Scr in group RM were lower than those in group RH (P<0.01). There was no significant difference between the contents of BUN and Scr at T2 and T1 in group S (P >0.05). In the other four groups, the contents of BUN and Scr at T2 were higher than those at T1 (P<0.05或0.01).5. The content of MDA and the activity of SOD in renal tissue: The content of MDA in other four groups were higher and the activity of SOD were lower than those in group S (P<0.01). The content of MDA were higher and the activity of SOD were lower in group RL, RM, RH than those in group M (P<0.05 or 0.01). The content of MDA were lower and the activity of SOD were higher in group RM, RH than those in group RL (P<0.01). The content of MDA was lower and the activity of SOD was higher in Group RH than that in RM (P<0.01).6. The activity of Ca2+-ATP in renal tissue: The activity of Ca2+-ATP in other four groups were lower than that in group S (P<0.05 or 0.01). The activity of Ca2+-ATP in Group RL , RM , RH were higher than that in group M (P<0.05 or 0.01). The activity of Ca2+-ATP in Group RM , RH were higher than that in group RL (P<0.05 or 0.01). The activity of Ca2+-ATP in Group RH was higher than that in group RM (P<0.01).Conclusion: Three doses of remifentanil via rat caudal vein infusion can attenuate renal ischemia-reperfusion injury. The protective effect of remifentanil with the continuous infusion at the speed of 1.0μg·kg-1·min-1 is the best in these three doses. The protective mechanism is possible related to remifentanil by inhibiting of lipid peroxidation, increasing the activity of Ca2+-ATP and reducing the calcium overload.
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