The Role Of Opioid Receptors In Remifentanil Attenuating Renal Ischemia/Reperfusion Injury In Rats

Objective: In the study, a rat model of renal ischemia/reperfusion injurywas established. To investigate the role of opioid receptors in remifentanilattenuating renal ischemia/reperfusion injury by observing the effects ofRemifentanil and naloxone on renal function, histology, superoxide dismutase(SOD) activity, malondialdehyde (MDA) content, the protein expression andactivity of protein kinase C(PKC).Methods: seventy-five male SD rats were randomly divided into5groups with15animals in each group: sham-operation group(S), model group(M), remifentanil group(R), naloxone group(N), naloxone+remifentanilgroup(NR). In group S, the bilateral renal were only exposed but their pedicleswere not clamped. In other four groups, the model of renal ischemia/reperfusion injury was prepared by occlusion of bilateral renal pedicles withatraumatic mini-clamps for45min, then the mini-clamps were removed for24h reperfusion. In group R and NR, the rats were infused remifentanil withthe speed of1.0μg· kg-1· min-1from15min before ischemia to30min afterreperfusion via the caudal vein, the same volume of saline was infused ingroup S, M and N. In group N and NR, The rats were injected naloxone(0.3mg/kg)20min before ischemia and35min after ischemia via the caudalvein, the same volume of saline was injected in group S, M and R. At24hafter reperfusion, a1-ml blood sample and a1-ml urine sample were collectedvia the femoral vein and urinary bladder, respectively, then centrifuged. Themeasurements for serum creatinine (sCr), blood urea nitrogen (BUN), urinaryN-acetyl β-D-glucosaminidase (NAG) and γ-glutamyl transpeptidase (γ-GT)were performed by using automatic biochemical analyzer, respectively. Allrats were killed at24h after reperfusion. The renal tissue samples wereobtained. Renal histological changes were observed by light microscope and transmission electron microscope. SOD activity was measured by the methodof xanthine oxidase. MDA content was measured by the method ofthiobarbituric. The protein expression of PKC was measured byimmunohistochemistry. PKC activity was measured by the method of ELISA.All data are expressed as means±standard deviation(S.D.). Means of groupswere compared by one-way analysis of variance (ANOVA), the level ofstatistical significance was accepted as P<0.05.Results:75rats were involved in the result analysis.1. Under light microscope: In group S, normal tissue was observed,without apparently histopathologic changes. The renal tubular epithelial cellwas not edema vacuolar degeneration, necrosis. The renal tubular lumen wasnot dilated. In group M, The renal tubular epithelial cells oedema, vacuolardegeneration, necrosis, tubular dilation and cast formation were predominant,and a large number of cell debris were observated in the lumen of renaltubulars. In group R, The renal tubular epithelial cells were lightly swollen,there was some degree of tubular dilation, and the merely slight cell debriswere observated in the lumen of renal tubulars. In group N and NR, the renalhistopathologic changes were similar with those in group M.2. Under transmission electron microscope: In group S, the ultrastructuresof the renal tubular epithelial cells were fundamentally normal. There was alarge number of mitochondria with no swollen, no vacuolar degeneration andno fracture, and intensive microvilli. In group M, the mitochondrial of therenal tubular epithelial cells were deformed and swollen, most of themitochondrial cristae were with fusion or deletion, and the microvilli weresparse. In group R, the mitochondrial of the renal tubular epithelial cells wereslightly expanded with the disappearance of some mitochondrial cristae, andthe microvilli were Intensive. In group N and NR, the ultrastructural changeswere similar with those in group M.3. sCr and BUN concentrations, urinary NAG and γ-GT levels: sCr andBUN concentrations, urinary NAG and γ-GT levels in other four groups werehigher as compared with group S (P<0.05or0.01). sCr and BUN concentrations, urinary NAG and γ-GT levels in group R were lower ascompared with group M(P<0.01). sCr and BUN concentrations, urinary NAGand γ-GT levels in group N and NR were higher as compared with groupR(P<0.01). No significant differences were seen in sCr and BUNconcentrations, urinary NAG and γ-GT levels among the three groups: groupM, N and NR (P>0.05).4. MDA contents and SOD activities in renal tissue: Compared with groupS, MDA contents were higher and SOD activities were lower in other fourgroups (P<0.05or0.01). Compared with group M, MDA contents were lowerand SOD activities were higher in group R(P<0.01).Compared with group R,MDA contents were higher and SOD activities were lower in group N and NR(P<0.05or0.01). No significant differences were seen in MDA contents andSOD activities in renal tissue among the three groups: group M, N and NR(P>0.05).5. The protein expressions of PKC in renal tissue: In group S, theexpressions of PKC were weak in the tubular epithelial cells, taking on amber.Compared with group S, cellular staining were profunduser in group M, N andNR, taking on yellow. In group R, PKC were strongly expressed in the tubularepithelial cells, taking on buffy. Compared with group S, the proteinexpressions of PKC in renal tissue were higher in group M, N and NR, but nosignificant differences were seen (P>0.05), the protein expressions of PKC inrenal tissue were significantly higher in group R (P<0.01). Compared withgroup M, the protein expressions of PKC in renal tissue were higher in groupR (P<0.01).Compared with group R, the protein expressions of PKC in renaltissue were lower in group N and NR (P<0.01). No significant differences ofthe expressions of PKC in renal tissue were seen among the three groups:group M, N and NR (P>0.05).6. PKC activities in renal tissue: Compared with group S, PKC activitieswere increased in other four groups (P<0.05or0.01). Compared with group M,PKC activities were increased in group R (P<0.01). Compared with group R,PKC activities were lower in group N and NR (P<0.01). No significant differences were seen in PKC activities in renal tissue among the three groups:group M, N and NR (P>0.05).Conclusion: Remifentanil attenuating renal ischemia/reperfusion injuryin rats is mediated by opioid receptors, which may be concerned with theaccumulation of ROS reduction in renal tissue and the expression and activityof PKC enhancement.