Abstract: Objective: To observe the inhibitory effect of ischemic postconditioning (I-postC) on the apoptosis of renal cells after limb ischemia reperfusion(LIR) in the rats, and to investigate the possible mechanisms.Methods: Thirty SD rats were randomly divided control group, ischemia-reperfusion group(IR group) and I-postC group(n=10).4 h ischemia and 4 h reperfusion with the rubber band in two hind limbs of the rats were performed to establish the models. In control group, the rubber band around the limb was loose and the blood flow was not blocked. As for I-postC group, before perfusion, 5 min ischemia and 5 min reperfusion were performed in the rats and repeated 3 times named I-post C. The levels of blood creatinine (Cr), blood urea nitrogen(BUN) and C-reactive protein (CRP) in plasma of the rats in various groups were measured by automatic biochemistry analyzer. The expressions of Bcl-2 protein and Bax protein in renal were detected by immunohistochemical method,and its quantitative results were observed with automatic image analysis system and the ratio of Bcl-2/Bax was calculated.The apoptotic cells in kidney tissue were determined by terminal-deoxynucleotidy1 transferase-mediated d-UTP nick end labeling (TUNEL) under laser scanning confocal microscope(LSCM).The ultrastructures of kidney tissue were observed under electron microscope.Results: Compared with control group, the levels of Cr,BUN and CRP in plasma of the rats in IR group and I-postC group were increased(P<0.05 or P<0.01);compared with IR group, the levels of Cr, BUN and CRP in plasma of the rats in I-postC group were decreased(P<0.01).Compared with control group,the expression levels Bax and Bcl-2 in kidney tissue of the rats in IR group and I-postC group were significantly increased (P<0.05 or P<0.01),and the ratios of Bcl-2/Bax were reduced(P<0.05);compared with IR group,the expression level of Bax in kidney tissue of the rats in I-postC group was decreased (P<0.05),the expression level of Bcl-2 was increased(P<0.01),and the ratio of Bcl-2/Bax was increased(P<0.05).Under laser confocal microscope,the number of apoptotic cells in kidney tissue of the rats in IR group was increased compared with control group;the number of apoptotic cells in I-postC group was decreased compared with IR group.Under transmission electron microscope,the changes in IR group were found as follows:renal proximal convoluted tubule epithelial cell nucleus vacuoles,increased lysosome and dense particle deposition, some mitochondria crest fracture or fuzzy; irregular and fusion, glomerular podocyte protuberance,mitochondrial cristae fracture and reducetion with vacuoles, rough endoplasmic reticulum expansion; the damage levels of renal tubular epithelial cells and glomerulus in I-postC group were improved compared with IR group.Conclusion: Limb ischemia reperfusion can induce the apoptosis of renal cells, I-postC can inhibit the apoptosis of renal cells,and it would be helpful to improve the kidney function.

Key words: kidney, apoptosis, reperfusion, ischemic postconditioning