年龄因素对低温减轻大鼠离体心脏缺血再灌注损伤的影响

Effects of age factors on hypothermia-induced reduction of ischemia-reperfusion injury in isolated rat hearts

目的评价年龄因素对低温减轻大鼠离体心脏缺血再灌注损伤的影响。方法清洁级健康老龄雄性SD大鼠，18～20月龄，体重400～600g，Langendorff模型制备成功的离体心脏24个，采用随机数字表法分为缺血再灌注组（AI／R组）和低温组（AH组），每组12个。青年大鼠，4～6月龄，体重280～350g，Langendofff模型制备成功的离体心脏24个，采用随机数字表法分为缺血再灌注组（YI／R组）和低温组（YH组），每组12个。采用停灌30rain，恢复灌注的方法制备缺血再灌注模型。缺血再灌注组整个过程维持37℃；低温组于再灌注即刻经34℃K—H缓冲液灌注120rain。于平衡灌流30rain（T0）、再灌注15、30、60和120min（T1-4）时记录HR、左室发展压（LVDP）、左室压力最大上升速率（＋dp／dtmax）和左室压力最小上升速率（＋dp／dtmin）。于T。时随机取6个离体心脏检测心肌组织ATP、SOD和MDA水平，采用TTC染色法测定心肌梗死面积。结果与YI／R组比较，YH组T1-4时HR降低，T4时心肌ATP和SOD水平升高，MDA含量和心肌梗死面积降低，AI／R组T0时HR、LVDP、＋dp／dtmax和＋dp／dtmin、T4时心肌ATP和SOD水平降低，MDA含量和心肌梗死面积增加（P〈0.05）；与YH组比较，AH组T。时HR、LVDP、＋dp／dtmax和＋dp／dtmin、T。时心肌ATP和SOD水平降低，MDA含量和心肌梗死面积增加（P〈0．05）；与AH组比较，AI／R组心肌ATP和SOD水平降低，MDA含量和心肌梗死面积增加（P〈0．05）。结论年龄因素影响低温减轻大鼠离体心脏缺血再灌注损伤的效果，对青年大鼠的心肌保护作用优于老龄大鼠。

Objective To evaluate the effects of age factors on hypothermia-induced reduction of ischemia-reperfusion （I/R） injury in isolated rat hearts. Methods Pathogen-free healthy aged male Sprague-Dawley rats, aged 18-20 months, weighing 400-600 g, and young rats, aged 4-6 months, weighing 280-350 g, were used in the study. After the animals were anesthetized with intraperitoneal chloral hydrate and heparinized, their hearts were excised and perfused with K-H solution in a Langendorff apparatus. Twenty-four isolated hearts of aged rats were assigned into 2 groups （n= 12 each） using a random number table ： I/R group （ group AI/R） and hypothermia group （ group AH）. Twenty-four isolated hearts of young rats were assigned into 2 groups （ n -- 12 each） using a random number table： I/R group （ group YI/R） and hypothermia group （group YH）. Perfusion was suspended for 30 min followed by 120 rain reperfusion to establish the model of I/R. The temperature was maintained at 37 ℃ during the whole process in AI/R and YI/R groups. The hearts were perfused with 34 ℃ K-H solution until 120 min of reperfusion starting from onset of reperfusion in AH and YH groups. At 30 min of equilibration （T0） and 15, 30, 60 and 120 rain of reperfusion （T1-4）, heart rate （HR）, left ventricular developed pressure （LVDP） , the maximum rate of increase in left ventricular pressure （ ＋dp/dtmax ） , and the minimum rate of increase in left ventricu- lar pressure （＋dp/dtnl.） were recorded. Six hearts from each group were randomly selected at T4, and myocardial specimens were obtained for determination of ATP, superoxide dismutase （SOD） and malondi- aldehyde （MDA） levels and myocardial infarct size （IS）. Results Compared with group YI/R, HR was significantly decreased at T14, ATP and SOD levels were increased, and the MDA content and myocardial IS were decreased in group YH, and the HR, LVDP, ＋dp/dta~~ and ＋dp/dtmi,~ at To and ATP and SOD levels at T4 were significantly decreased, and the MDA content and myocardial IS were increased in group AI/R （P〈0.05）. Compared with group YH, HR, LVDP, ＋dp/dt and ＋dp/dtmin at To and ATP and SOD levels at T4 were significantly decreased, and the MDA content and myocardial IS were increased in group AH （P〈0. 05）. Compared with group AH, the levels of ATP and SOD were significantly decreased, and the MDA content and myocardial IS were increased in group AI/R （P〈0.05）. Conclusion Age factors affect the efficacy of hypothermia in reducing I/R injury in isolated rat hearts, and hypothermia provides better eardioprotection for young rats than for aged rats.