缺血后处理减轻犬肾缺血再灌注损伤的作用

Effects of ischemic postconditioning on renal ischemia-reperfusion injury in dogs

目的探讨缺血后处理减轻犬肾缺血再灌注损伤的作用及其相关机制。方法随机将犬分为假手术组、缺血再灌注组和缺血后处理组，每组5只。假手术组：犬麻醉后，取其腹正中切口进入腹腔，游离双侧肾脏，切除右肾后，关腹。缺血再灌注组：手术操作与假手术组相同，仅在切除右肾和游离左肾之后，将左肾动、静脉夹闭60min，然后开放血管。缺血后处理组：手术操作与缺血再灌注组相同，仅在肾动、静脉被夹闭60min后，以再灌注（开放血管）30s、夹闭血管30S为1个循环，共进行6次循环，然后完全放开血管。分别于术后24、48及72h采集犬静脉血2ml，使用全自动生化分析仪测定各组犬血清肌酐（Cr）和尿素氮（BUN）水平；术后第3天取犬肾组织，采用硫代巴比妥酸法测定丙二醛（MDA）含量，采用黄嘌呤氧化酶法测定超氧化物歧化酶（SOD）活性，采用化学比色法测定髓过氧化物酶（MPO）活性，并观察犬肾组织的病理改变和细胞凋亡情况。结果术后各时间点，缺血再灌注组、缺血后处理组和假手术组犬的血清Cr和BUN水平均依次降低，3组问比较，差异均有统计学意义（P〈0．05）。术后第3天，缺血再灌注组、缺血后处理组和假手术组犬肾组织中SOD活性依次升高，而MDA含量和MPO活性均依次降低，3组间比较，差异均有统计学意义（P〈0．05）。假手术组肾小球和肾小管结构正常，未见明显病理改变；缺血再灌注组肾间质水肿，大量炎症细胞浸润，肾小管上皮细胞刷状缘消失，大量上皮细胞坏死、脱落，管腔扩张，其中可见大量管型；缺血后处理组可见肾间质轻度水肿，肾小管上皮细胞扁平，部分刷状缘消失、坏死，偶见管型，管周血管有少量淤血。假手术组、缺血再灌注组、缺血后处理组犬肾的细胞凋亡指数分别为2．7±1．3、28．4±6．2N15．4±4．1，3组间比较，差异均有统计学意义（P〈0．05）。结论缺血后处理能减轻犬肾缺血再灌注损伤，其机制可能与缺血后处理减少氧自由基的产生、抑制细胞凋亡及减少炎症细胞浸润有关。

Objective To investigate the effects of ischemic postconditioning （IPO） on the acute renal ischemia/reperfusion （I/R） injury in dogs. Methods Fifteen adult male mongrel dogs were randomly divided into three groups with 5 animals in each group. In sham operation group （S）, after the dogs were anesthetized, the midline laparotomy was made and right nephrectomy was performed; In I/R group, animals were subjected to the similar surgical procedures, except that the left renal vessels were clamped; In IPO group, the IPO was induced by 6 cycles of reperfusion （30 s） and ischemia （30 s） after 60 rain renal ischemia before reperfusion completely. Blood samples were obtained for determination of blood creatinine （Cr） and urea nitrogen （BUN） concentrations before operation and at 24, 48 and 72 h after operation. The dogs were killed at the thirdday after operation and left kidneys were removed for determination of SOD activity and MDA and MPO concentrations. The apoptosis in the nephridial tissue was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） and apoptotic index （AI） was calculated. The changes of renaltissue were examined by a microscope. Results Blood Cr and BUN concentrations in I/R group, IPO group and S group were decreased in turn after operation （P〈0. 05）. MDA and MPO concentrations were decreased significantly, SOD activity was significantly increased and AI was decreased significantly in IPO group as compared with I/R group at 72 h after operation （P〈0. 05）. Microscopic examination showed that there was no renal injury in S group and renal I/P, resulted in tubular necrosis, medullary hemorrhage congestion and proteinaceous casts in I/R group. The renal I/R injury was significantly attenuated by IPO. In S group, IPO group and I/R group the renal AI was 2. 7 ±1.3, 28. 4 ± 6. 2 and 15.4 ± 4. 1 respectively （P〈0. 05）. Conclusion IPO can attenuate renal damage induced by I/R by inhibiting oxidative stress and apoptosis and decreasing inflammation.