改进的TTC染色法显示大鼠心肌缺血再灌注损伤

目的比较应用不同2,3,5-氯化三苯基四氮唑(TTC)染色方法对大鼠心肌缺血再灌注损伤后梗死面积的检测效果。方法将20只SD大鼠(雄性,8周龄,体重250~300 g)按随机数字表法分为两组,每组10只。A组:传统TTC染色法组;B组:改进后的TTC染色法组,分别进行大鼠心肌染色,随后计算心肌梗死面积及测定血清cTnI浓度水平。结果 A组和B组均能较好地标记梗死心肌;A组和B组心肌梗死面积百分比无统计学差异(48.69%±5.37%vs.47.41%±3.28%,P0.05);A组和B组血清cTnI浓度水平无统计学差异(4.51±0.88 ng/mL vs.4.70±0.71 ng/mL,P0.05);但B组心肌切片染色色泽对比度及心肌非梗死区与梗死区区分度均高于A组。结论改进后的心肌TTC染色法采用在体染色,不仅操作简便,节省了实验时间和经费,而且提高了染色效果,能更准确地反映心肌缺血再灌注损伤的程度。因此改进后的心肌TTC染色法是一种经济、简便、快捷、高效的染色方法。     

Cardioprotective effect of magnesium chloride in experimental acute myocardial infarction

Cardioprotective role of intravenous administration of magnesium chloride was evaluated in rabbits by biochemical and histopathological parameters. Myocardial damage was induced by injecting (i.v.) isoprenaline 1, 2.5, 5 and 7.5 mg/kg body weight of animal. There was a dose dependent increase in the activity of cardiac enzyme creatinine kinase CK (C Max). Maximal elevation of CK (C Max) was observed with 2.5 mg isoprenaline. The mean T-max (mean of the time duration in hr at which maximum creatinine kinase activity of individual rabbit was observed in a group) shifted early, significantly with 2.5, 5 and 7.5 mg isoprenaline compared to control group. Histopathologically, myocardial damage was quite significant in 2.5 mg isoprenaline subgroup of animals. A mortality of 29% was observed in animals injected with 5 and 7.5 mg isoprenaline, whereas all animals subjected with 1 and 2.5 mg isoprenaline were alive for 72 hr. Considering the data on serial determination of cardiac enzyme CK and histopathological changes, 2.5 mg isoprenaline was chosen as standard dose to study efficacy of cardioprotection by gold standard verapamil and magnesium chloride. Verapamil (5 microM) injected prior to 2.5 mg isoprenaline administration revealed significant reduction of CK (C Max) activity (P < 0.05) compared to animals infused with isoprenaline alone. T-max value did not show any alteration in both the groups. Histopathological findings showed no areas of necrosis and cellular infiltrates in animals primed with 2.5 mg isoprenaline following verapamil. Highly significant reduction in CK (C-max) activity was observed in animals administered with 40 mg magnesium chloride prior to isoprenaline compared to animals treated with isoprenaline alone (P < 0.001). In addition to this, significant delay in T-max of CK activity was observed in group treated with 40 mg magnesium chloride and isoprenaline compared to group treated with only isoprenaline (P < 0.01). The study clearly highlighted and confirmed the valuable role of magnesium chloride as cardioprotective agent.     

TTC法测定红豆杉细胞活力

取悬浮培养红豆杉细胞,加入TTC溶液及缓冲液,避光保存后,以蒸馏水洗细胞3次,再用乙醇使细胞完全脱色后,测波长485 nm处吸光值.结果以0.4%的TTC溶液,0.1 mol@L-1(pH 7.0)的Na2HPO4-NaH2PO4缓冲液,25℃处理13～16 h为最适..     

Features of myocardial remodeling in the most acute phase of experimental myocardial infarction

The features of early postischemic cardiac remodeling have been well studied both in clinical settings and in experiments. However, the data on the course of this process in the first 60 min after occlusion are scarcely available in the literature. In experiments on rats, in which acute myocardial ischemia was reproduced by one-stage ligation of the left coronary artery, echocardiography showed a sharp decline in the left ventricular systolic function during the first minutes of ischemia: after 20 min, the ejection fraction (EF) decreased from 84.5 (79.3?C89.2) to 51.7 (50.2?C54.4)%, p < 0.05; the shortening fraction (SF) decreased from 52.6 (47.8?C59.3) to 26.5 (25.9?C28.1)%, p < 0.05; and the end-systolic dimension (ESD) of the left ventricle of the heart increased from 1.90 (1.70?C2.20) to 3.80 (3.50?C4.10) mm, p < 0.05, whereas no statistically significant disorder of the left ventricular systolic function was observed in sham-operated animals during the observation period (60 min). A gradual relative improvement in the systolic function has been observed in the period from the 20th to the 60th minute of ischemia. After 60 min of ischemia, all the echocardiographic parameters differed significantly (p < 0.05) from those recorded after 10?C20 min of the ischemic period: EF, 62.4 (59.0?C64.3)%; SF, 33.7 (31.1?C35.2)%; ESD, 3.10 (2.80?C3.40) mm, etc. The analysis of the results suggests that the maximum reduction in the left ventricular EF observed in our experiments coincides in time with the arrhythmogenesis peak, i.e., with the maximal risk of sudden cardiac death.     

Occurrence of a terminal vascularisation after experimental myocardial infarction

Physiological data indicate a residual vascularisation within ischemic myocardial regions where necrosis of most cells have been reported to occur after myocardial infarction. We therefore studied, by means of immunohistochemistry, computer-assisted morphometry, and electron microscopy, the terminal vascularisation in correlation to cardiomyocytes in ten canine hearts 1 and 3 weeks after occlusion of the left anterior descending (LAD) coronary artery. In comparison to non-infarcted myocardium we found the following alterations in infarcted myocardium: (1) the area density of cardiomyocytes decreased from 98% (control) to 7.9% (1 week after occlusion) and to 2.7% (3 weeks after occlusion); (2) the number of capillaries was diminished to 11.6% and to 2.6%; respectively; (3) smooth muscle α-actin was induced in endothelial (EC) cells of the microvessels; and (4) terminal resistance vessels increased 11-fold and 20-fold in number, respectively. Our findings confirm the necrosis of the vast majority of cardiomyocytes and capillaries within the first 3 weeks after myocardial infarction. Besides a small number of capillaries, many terminal resistance vessels, however, seem to persist in the scarring infarcted tissue. The occurrence of these microvessels is supposed to be important for the granulation tissue as well as for the control and regulation of a residual blood supply during scar formation.