| Objective To establish a model of renal ischemia-reperfusion in rats. To investigate the effect of ischemic preconditioning, ischemic postconditioning, ulinastatin pretreatment and ischemic postconditioning on the renal ischemia-reperfusion (I/R) injury and its mechanism. To evaluate the diagnostic significance of urine alpha 1-microglobulin (α1-MG) and Beta 2-microglobulin (β2-MG) on the early stage renal impairment.Methods Thirty-six male SD rats weighing 250-280g were randomly allocated into 6 groups (n=6 each): groupâ… sham operation (S); groupâ…¡I/R; groupâ…¢ischemic preconditioning+I/R (IP); groupâ…£I/R+ischemic postconditioning(IPo); groupâ…¤ulinastatin+ I/R(U) ; groupâ…¥ulinastatin+ I/R+ischemic postconditioning(U+IPo). The rats were anesthetized with intraperitoneal chloral hydrate 300 mg·kg-1. Bilateral kidneys were exposed through midline incision and bilateral renal pedicels were occluded 45 min with atraumatic mini-clamp then unclamped for 6 h. The kidneys turned kermesinus. In S group the kidneys were exposed but their pedicles were not clamped. In IP group, The kidneys were induced by 3 circles of ischemia (5 min) separated by reperfusion (5 min) before ischemia-reperfusion injury. In IPo group, 45 min ischemia was followed by three 10 s episodes of ischemia at 10 s intervals for reperfusion. In U group, ulinastatin 2×104 U·kg-1 was given i.v. 30 min before ischemia. In U+IPo group, ulinastatin 2×104 U·kg-1 was given i.v. 30 min before ischemia then 45 min ischemia was followed by three 10 s episodes of ischemia at 10 s intervals for reperfusion.The animals were killed at 6 h of reperfusion. Blood samples were taken from heart for determination of urea nitrogen(BUN), serum creatinine(Cr) and uric acid(UA) concentrations. Urine samples were taken from urinary bladder for determination ofα1-MG andβ2-MG contents. Kidneys were removed immediately for determination of MDA level and SOD activity, the expression of Bcl-2 and Bax protein by immuno- histochemistry assay and Bcl-2 mRNA and Bax mRNA by RT-PCR and for microscopic examination. The apoptosis in the nephridial tissue was assessed using TUNEL and apoptotic index(AI) was calculated.Results After I/R the Cr and BUN concentrations, theα1-MG,β2-MG and MDA contents, the expression of Bax and Bax mRNA and the AI were all significantly increased while the SOD activity, the expression of Bcl-2,Bcl-2 mRNA and the Bcl-2 mRNA/Bax mRNA ratio were significantly decreased as compared to the S group(P< 0.05). The Cr and BUN concentrations, theα1-MG,β2-MG and MDA contents, the expression of Bax and Bax mRNA and the AI were all significantly lower while the SOD activity, the expression of Bcl-2,Bcl-2 mRNA and the Bcl-2 mRNA/Bax mRNA ratio were significantly higher in IP, IPo, U and U+IPo group(groupâ…¢,â…£,â…¤,â…¥) as compared with groupâ…¡(I/R) (P<0.05). The histologic damage induced by I/R were significantly ameliorated. There was no significant difference in UA levels among the 6 group.The serum Cr levels was significantly lower in U+IPo group than in IP and U group(P<0.05). The Bcl-2 mRNA/Bax mRNA ratio was significantly increased in U and U+IPo group as compared to the IP and IPo group (P<0.05). The MDA contents was significantly lower in U+IPo group than in U group(P<0.05). The expression of Bcl-2 mRNA was significantly higer in U+IPo group as compared to the IP and IPo group(P<0.05). There were no significant difference in the rest indexes among the IP, IPo, U and U+IPo group.Conclusion1 IP, IPo, ulinastatin pretreatment(U) and U+IPo can reduce the risk of renal dysfunction and injury associated with renal I/R injury by reducing apoptosis through enhancement SOD activity. IP, IPo, U and U+IPo can inhibit apoptosis of renal cells induced by I/R by up-regulating Bcl-2 gene, increasing the expression of Bcl-2 protein, down-regulating Bax gene, decreasing the Bax protein and regulating the Bcl-2 /Bax ratio accordingly. 2 IP, IPo, U and U+IPo can protect the kidney against ischemia-referfusion injury in rats and U+IPo is more effective.
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