控制性低压灌注对兔脊髓缺血再灌注时磷酸化Akt和磷酸化ERK表达的影响

Effect of controlled low perfusion pressure on expression of phosphor-Akt and phosphor-ERK following spinal ischemia-reperfusion in rabbits

目的探讨控制性低压灌注对兔脊髓缺血再灌注时磷酸化蛋白质丝氨酸苏氨酸激酶（p-Akt）和磷酸化细胞外信号调节激酶1／2（p-ERK1／2）表达的影响。方法雄性日本大耳白兔36只，3月龄，体重2．0—2．5奴，采用随机数字表法，将其随机分为3组（n=12）：假手术组（s组）、脊髓缺血再灌注组（I／R组）和控制性低压灌注组（LP组）。I／R组和LP组采用在肾动脉下水平阻断腹主动脉25min行再灌注的方法制备脊髓缺血再灌注损伤模型。LP组再灌注10min期间维持腹主动脉远端血压45～55mmHg。分别于再灌注1、3、7、28d时进行后肢运动功能功能。每组于再灌注1d时处死动物，取脊髓组织，测定p-Akt、p-ERK1／2表达及神经元凋亡情况，计算凋亡指数，电镜下观察病理学结果。结果与S组比较，I／R组后肢运动功能评分降低，p-Akt和p-ERK1／2表达上调，凋亡指数升高（P〈0．05）；与I／R组比较，LP组后肢运动功能评分升高，p-Akt和p-ERK1／2表达上调，凋亡指数降低（P〈0．05）。LP组脊髓组织病理学损伤程度轻于I／R组。结论控制性低压灌注减轻兔脊髓缺血再灌注损伤的机制与激活Akt及ERK1／2，抑制神经元凋亡有关。

Objective To investigate the effect of controlled low perfusion pressure on expression of phosphor-Akt （p-Akt） and phosphor-ERK1/2 （p-ERK1/2） following spinal ischemia-reperfusion （I/R） in rabbits. Methods Thirty-six Japanese long-ear white rabbits aged 3 months weighing 2.0-2.5 kg were randomly divided into 3 groups （ n = 12 each） ： group sham operation （group S） ; group spinal I/R （group I/R） and group controlled low perfusion pressure （group LP）. Auricular artery and femoral artery were cannulated for proximal and distal BP monitoring. A 4F catheter with a balloon at the tip was inserted into abdominal aorta. The tip was positioned 1 cm below left renal artery. Spinal ischemia was induced by inflating the balloon until the distal MAP 〈 20 mm Hg, and maintained for 25 min. During the first 10 min of reperfusion the distal MAP was increased to 45-55 mm Hg by partially deflating the balloon. Then the balloon was fully deflated to allow complete reperfusion. The function of lower limbs was assessed with Tarlov score （0 = no detectable movement, 4 = normal function） at 1, 3, 7, 28 d of reperfusion. Au the animals were sacrificed at 1 d of reperfusion in each group. The lumbar segment I~_5 of the spinal cord was removed for microscopic examination and determination of expression of p-Akt and p-ERK1/2 by immuno-histochemistry） and detection of neuronal apoptosis in dorsal horn （by TUNEL）. Results Spinal I/R significantly decreased Tarlov scores, and increased the number of apoptotic cells and expression of p-Akt and p- ERK1/2 in group I/R as compared with group S. Low perfusion pressure during the 10 min at the beginning of reperfusion significantly increased Tarlov scores, decreased apoptotic index and further increased p-Akt and p-ERK1/2 expression in group LP compared with group I/R. The histopathological damage in the spinal cord was attenuated in group LP. Conclusion Controlled low perfusion pressure can reduce the spinal cord I/R injury by acti- vating Akt and ERK1/2 and decreasing neuronal apoptosis.