| Objective: Ischemic postconditioning (IpostC) is an important measurefor protecting the heart, but the cardioprotection difference of different agehad less studied in recent years. In this study, we will focus on the observationof protective effect of ischemic postconditioning on isolated rat heart,especially observe whether there are differences of cardioprotection amongthe rats of different.Method: Healthy male SD rats (provided by the Experimental AnimalResearch Center of Hebei Medical University), including the Infancy rats(1-2months,150-200g),Young rats (4-5months,300-350g),Middle-aged rats(14-16months,600-700g).The rats of same age are randomly divided into twotreatment groups: ischemic/reperfusion group and ischemic postconditioninggroup,6cases in each group. Anesthetize the rats and quickly remove theheart from rat, then perfuse the heart using Langendorff system with perfusate(K-H solution) prepared in the same day for freshly K-H solution.Then recordthe index including HR, LVDP, LVEDP, dp/dtmax and dp/dtmin withpolygraph. The isolated rats hearts in I/R group were perfused30min forbaseline,30min for ischemia and the120min for reperfusion, while theisolated rats hearts in IpostC group were perfused30min for baseline,30minfor ischemia, and given6cycles of10s reperfusion/10s ischemia beforereperfusion followed by sustained and reperfusion. In the course of theexperiment, perfusate was reserved respectively at balance perfused30min,reperfusion1min,3min,5min,10min,20min,30min,60min,120min forassessing coronary flow and determination of CK and LDH activity,after twohours reperfusion the heart was taken down for measurement of myocardiuminfarcted size with TTC staining. Results:1Hemodynamic parameters(1) The comparisons within each age group between different treatmentsAt the end of baseline30min, that was before ischemia: infancy, young andthe middle-aged groups: LVDP, dp/dtmax the dp/dtmin between I/R group andIpostC group, there were no significant differences (P>0.05);At the end of reperfusion for120min:The infancy group: the LVDP, recovery rate of dp/dtmax and dp/dtmin inIpostC group were significantly higher than in I/R groups (P<0.05);The young group: recovery rate of dp/dtmax in IpostC group wassignificantly higher than in I/R groups (P<0.05); but recovery rate of theLVDP and dp/dtmin between IpostC group and I/R group, there were nosignificant differences (P>0.05).The middle-aged group: recovery rate of LVDP, dp/dtmax and dp/dtminin IpostC group were no significant differences compared with I/R groups(P>0.05).(2) The comparison between age groups under the same protocolAt end of basline30min, that was before ischemia:The LVDP, dp/dtmax and dp/dtmin in the young group were higher thanthe corresponding infancy group (P<0.05) and the middle-aged group(P<0.05); furthermore,the LVDP, dp/dtmax and dp/dtmin in the middle-agedgroup were higher than that in the corresponding infancy group (P<0.05).At the end of reperfusion for120min:The recovery rate of LVDP, dp/dtmax and dp/dtmin in the I/R group ofboth infancy and young group were not different (P>0.05); the recovery rateof LVDP in the infancy and young group was higher than in the middle-agedgroup (P<0.05);The recovery rate of LVDP, dp/dtmax and dp/dtmin in IpostC groupsbetween infancy group and young group were not significantdifferent(P>0.05); the LVDP, dp/dtmax and dp/dtmin recovery rate of infancygroup and young group were higher than that in the middle-aged group(P<0.05). 2The arrhythmias observedDuring the baseline, perfused rat heart in all age groups had noarrhythmia, but all age groups had arrhythmia during the reperfusion period,including premature ventricular contractions, premature ventricular bigeminyand paroxysmal ventricular tachycardia, which usually occurs within the first20min of reperfusion period, they showed no significant differences betweenthe various age groups about the incidence of arrhythmias (P>0.05).3Creatine kinase (CK) and Lactate Dehydrogenase (LDH) observation(1) The comparisons within each age group between different protocolThis study shows that the activity of CK and LDH (IU/ml) within eachage group had no significant difference(P>0.05) at the end of the baselineperfused; the activity of LDH between the I/R group and IpostC groups at thefirst20min of reperfusion was increased; the LDH activity of the infancy andthe young IpostC group was lower than that in I/R group (P<0.05), but theactivity of LDH between I/R group with IpostC of group in middle-agedgroup was not different (P>0.05). Peaks of CK activity in each age groupswere within10min of reperfusion, and CK activity in each groups atreperfusion3min was significantly higher than that in the baseline30min(P<0.05), than began to decline.(2) The comparison between age groups under the same protocolI/R group: the CK and LDH activity at the baseline30min betweeninfancy group and young group and the middle-aged group was no significantdifference (P>0.05). After reperfusion, the CK and LDH activity in each agegroup was rised, the LDH activity at reperfusion3min in the middle-agedgroup was significantly higher than that of the infancy group and young group(P<0.05);IpostC groups: the CK and LDH activity at the baseline30min betweeninfancy group and young group and the middle-aged group was not significantdifferent (P>0.05). After reperfusion,the CK and LDH activity of each timepoint in infancy group was significantly lower than that in the young andmiddle-aged groups. The CK and LDH peaks of the middle-aged rats was higher than that in the infancy group and young group (P<0.05).The CK levelsin middle-aged rats was higher than that in the infancy group and young groupat end of baseline30min and peak of CK activity.4Myocardial infarction size(1) The comparisons within each age group between different protocolIn IpostC group of infancy and young rats, myocardial infarct size wassignificantly smaller than of the I/R group (13.26%±2.48%vs21.91%±8.56%,P<0.05;16.96%±1.79%vs41.98%±3.16%, P<0.05);compared with the I/R group in the middle-aged, the myocardial infarct sizeof IpostC group was not significant different (36.20%±5.38%vs42.02%±3.76%,P>0.05).(2) The comparison between age groups under the same protocolI/R groups: the myocardial infarct size in infancy group was significantlysmaller than that in the young group or middle-aged group (21.91%±8.56%vs41.98%±3.16%,P＜0.05;21.91%±8.56%vs42.02%±3.76%,P<0.05); therewas not significant different about myocardial infarct size between younggroup and the middle-aged group,(41.98%±3.16%vs42.02%±3.76%,P>0.05);IpostC groups: the myocardial infarct size in infancy group was smallerthan that in the young group (13.26%±2.48%vs16.96%±1.79%, P<0.05) andin the middle-aged group (13.26%±2.48%vs36.20%±5.38%, P<0.05); themyocardial infarct size in young group was significantly less than that in themiddle-aged group (16.96%±1.79%vs36.20%±5.38%, P<0.05).Conclusions:1Under the same ischemic injury, the myocardial infarct size in infancygroup was significantly smaller than that in the young group and middle-agedgroup; the LVDP recovery rate in infancy and young group was higher thanthat in the middle-aged group (P<0.05).2IpostC could significantly reduce myocardial infarct size in infancy andyoung rats, but could not reduce significantly myocardial infarct size ofmiddle-aged rats. 3In IpostC group of infancy and young rat hearts, the release ofmyocardial injury markers (CK, LDH) tended to come down, but this trendwas not obvious in middle-aged rat hearts.4IpostC could significantly increase recovery rates of LVDP, dp/dtmaxand dp/dtmin in the infancy rats and the recovery rate of dp/dtmax in theyoung rats. However, IpostC could not significantly improve the recovery ofcardiac function in middle-aged rats. |
PDF Full Text Request