| Objective:More and more studies focus on the factors which can affectthe pathogenesis, development, treatment and prognosis of ischemic heartdisease with the yearly increase in the morbidity and mortality. Among thesefactors, the protective effect against ischemia-reperfusion injury of ischemicpreconditioning and post-conditioning in many animals have been confirmed.Early studies found the different protective effect of ischemicpost-conditioning on rat hearts of different ages from ischemia-reperfusioninjury, and the absence of ischemic preconditioning in rat myocardium inaging hearts has been confirmed. However, there was less report about theprotective effect of ischemic preconditioning on rat heart of different age, andthere are still some debates on the additive effect of preconditioning andpostconditioning.This study was designed to find out whether there wasdifference in the protective effect of ischemic preconditioning in rats ofdifferent ages,furthermore,to observe whether there was additive effect ofischemic preconditioning and postconditioning in rat hearts of different agesin order to provide theoretical basis to the different protection measures takenon patients of yong and old age.Methods:120healthy male SD rats(provided by the ExperimentalAnimal Research Center of Hebei Medical University) included40infacyrats of1-2months(150-200g),40young rats of4-5months (300-350g) and40middle-aged rats of14-16months(600-700g). Every age group wasrandomly divided into four treatment groups: ischemia-reperfusion group(I/R group), ischemic preconditioning group(IpreC group), ischemicpostconditioning group(IpostC group) and ischemic preconditioning+post-processing group(IpostC+IpreC group),there were6rats in everytreatment group. Langendorff isolated heart perfusion system was used for perfusion and multi polygraph to collect hemodynamics as HR, LVDPmin,LVDPmax, dp/dtmax, dp/dtmin and so on. During the experiment,perfusate at different time points:balance perfused30min, reperfusion1min,3min,5min,10min,20min,30min,60min,120min was collected to assesscoronary flow and determine the activity of CK and LDH. With TTCstaining, myocardial infarction range was measured after reperfusion.Results:1Infancy group(1)The myocardial infarct sizeThe myocardial infarct size of infancy rats in IpreC group, IpostC groupand IpostC+IpreC group was less than that in I/R group (P<0.05); but therewas no difference between every two groups(P>0.05).(2)Cardiac enzymesThe activity of CK and LDH in IpreC group, IpostC group and IpostC+IpreC group was less than I/R group (P<0.05); but there was no differencebetween every two groups(P>0.05).(3)Hemodynamic parametersThe recovery rate of LVDP, dp/dtmax, dp/dtmin in IpreC group,IpostC group and IpostC+IpreC group was better than I/R group (P<0.05);The recovery rate of LVDP, dp/dtmax, dp/dtmin in IpostC group was betterthan that of the IpreC group; there was no difference between the IpostCgroup and the IpostC+IpreC group.2Youth Group:(1)The myocardial infarct sizeThe myocardial infarct size of young rats in IpreC group, IpostC groupand IpostC+IpreC group was less than I/R group (P<0.05); but there was nodifference between every two groups(P>0.05).(2)Cardiac enzymesThe activity of CK and LDH in IpreC group, IpostC group and IpostC+IpreC group was less than I/R group (P<0.05); but there was no differencebetween every two groups(P>0.05). (3)Hemodynamic parametersThe recovery rate of LVDP, dp/dtmax, dp/dtmin in IpreC group,IpostC group and IpostC+IpreC group was better than I/R group (P<0.05);there was no difference among the IpostC group,the IpreC group and theIpostC+IpreC group(P>0.05).3Middle-aged group:(1)The myocardial infarct sizeThe myocardial infarct size of middle-aged rats in IpreC group, IpostCgroup and IpostC+IpreC group was not different with the I/R group(P>0.05); and there was no difference among these three groups(P>0.05).(2)Cardiac enzymesThe activity of CK and LDH in IpreC group, IpostC group and IpostC+IpreC group was no less than the I/R group (P>0.05); and there was nodifference among these three groups(P>0.05).(3)Hemodynamic parametersThe recovery rate of LVDP, dp/dtmax, dp/dtmin in IpreC group,IpostC group and IpostC+IpreC group was no better than I/R group(P>0.05); there was no difference between every two groups of the IpostCgroup,the IpreC group and the IpostC+IpreC group(P>0.05).4Comparison of myocardial injury in the different age group from the sameischemic burdenAt the end of balance perfusion: hemodynamics LVDP, dp/dtmax anddp/dtmin of the middle-aged group was less than the infancy group andyoung group(P<0.05),but there was no statistical difference between theinfancy group and the young group(P>0.05). The cardiac enzymes CK, LDHactivity of three age groups had no significant difference (P>0.05).At the end of2hours’ reperfusion after30minutes’ ischemia, we couldfind different tolerance to ischemic injury in three age groups:(1)The myocardial infarct sizeThe infarct size in infancy group was significantly smaller than that ofyoung groups(P<0.05) and middle-aged group(P<0.05),but there was no statistically significant difference between young group and the middle-agedgroup in myocardial infarct size (P>0.05).(2)Cardiac enzymesThe activity of CK and LDH in infancy group and young group waslower than in the middle-aged group (P<0.05), that of the infancy group waslower than the young group (P<0.05).(3)Hemodynamic parametersThe recovery rate of LVDP dp/dtmax and dp/dtmin in infancy groupand young group was lower than the middle-aged group (P<0.05), but therewas no difference between the infancy group and young group (P>0.05).Conclusion:1Ischemic preconditioning and ischemic postconditioning could reducemyocardial infarct size in hearts of young rats,reduce the activity of CK andLDH, increase LVDP, dp/dtmax, dp/dtmin recovery rate, but there was noadditive effect.Furthermore,there was no difference of ischemic preconditio-ning and ischemic postconditioning in the protection of the myocardialinfarct size in infancy rats.2Ischemia preconditioning and ischemic postconditioning could reducemyocardial infarct size in young rats, reducing cardiac enzymes CK,LDH,and partly improve the recovery rate of LVDP and dp/dtmax, andthere was no additive effect. Furthermore,there was no significant differenceof ischemic preconditioning and ischemic postconditioning in the protectionof the myocardial infarct size in young rats.3Ischemic preconditioning and ischemic postconditioning could notsignificantly reduce infarct size in middle-aged rats,both the release ofcardiac enzymes CK, LDH and the recovery rate of LVDP, dp/dtmax, dp/dtmin shwed no protective effect of ischemic preconditioning and ischemicpostconditioning on middle-aged rats. Given both provided no protectiveeffect in the aspects mentioned above,either.4Given the same degree of ischemia, injury indicators in three age groupsshowed that infarct size in the hearts of infancy group rat was significantly smaller than the young group and middle-aged group, while the recovery rateof LVDP, dp/dtmax, dp/dtmin in infancy group and young group werehigher than that in the middle-aged group. |
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