慢性心力衰竭大鼠主动脉舒缩功能的变化及其机制

Alterations in aortic vasomotor function in rats with chronic heart failure and its mechanism

为探讨心力衰竭诱导的血管舒缩功能紊乱的相关机制,本实验对心梗后大鼠慢性心力衰竭(chronic heart failure,CHF)模型胸主动脉血管环的舒缩功能变化及可能的病理学机制进行了研究。将Sprague-Dawley大鼠随机分为两组:假手术(sham)组和慢性心衰(CHF)组。通过冠脉结扎法制作大鼠CHF模型。手术10周后,检测大鼠血流动力学指标及相关参数,之后迅速取出心脏并称重,TTC染色法检测心梗面积。制备大鼠胸主动脉环,利用敏感的肌张力描记技术,比较sham组和CHF组胸主动脉环的舒缩功能,观察血管环对KCl、CaCl2、苯肾上腺素(phenyle phrine,PE)和咖啡因(caffeine)的收缩反应以及对乙酰胆碱(acetylcholine,ACh)的舒张反应。并进一步研究一氧化氮合酶(nitricoxide synthase,NOS)抑制剂N-硝基-L-精氨酸甲酯(N-nitrl-L-arginine methylester,L-NAME)和非选择性环氧合酶(cyclooxy genase,COX)抑制剂吲哚美辛(indomethacin,Indo)对两组胸主动脉环ACh的反应曲线的影响。结果显示:(1)与sham组相比,CHF组大鼠胸主动脉环对血管收缩剂KCl(5～100mmol/L)和PE(1×10-8～3×10-4mol/L)的反应性明显提高,对血管舒张剂ACh(1×10-12～1×10-4mol/L)的反应性显著性降低(P<0.01,P<0.05);(2)L-NAME(1mmol/L)预处理后,CHF组血管对ACh(1×10-7～1×10-4mol/L)介导的内皮依赖性收缩明显增强(P<0.05),加入Indo(10μmol/L)后该现象消失;(3)与Indo未处理组相比,Indo(10μmol/L)预处理后,CHF组血管对ACh(1×10-12～1×10-4mol/L)介导的舒张反应明显增强(P<0.05);(4)在无钙K-H液中,与sham组相比,CHF组血管对CaCl2(1×10-4～3×10-2mol/L)介导的钙依赖性收缩曲线明显左移(P<0.05);caffeine(30mmol/L)诱导的血管收缩未见显著性变化。以上结果表明,CHF大鼠的胸主动脉血管环收缩异常与内皮功能障碍有关,其机制可能是通过血管内皮细胞COX途径提高内皮收缩因子,和(或)通过电压依赖性钙通道增加外钙流入引起血管收缩性能提高。

The aim of the present study was to investigate the alterations in thoracic aortic vasomotor function in rats with chronic heart failure（CHF） post myocardial infarction（MI）,and then explored the possible mechanism of pathological changes.Male SpragueDawley rats were divided into sham and CHF groups randomly.The CHF model group of rats was generated by ligating the left anterior descending artery.In sham-operated rats the ligation was placed but not tightened.A total of 20 rats underwent either sham-operated（n=8） or surgery for MI（n=12）.All sham-operated rats survived the surgical procedure and the post-surgical period,whereas total mortality among MI-rats was 25%（3 out of 12）.Only MI-rats with infarct-size 30% of the left ventricle（LV） were included for analysis（8 out of 9）.Ten weeks after surgery,rats were anaesthetized for hemodynamic measurements,which contains systolic pressure,diastolic pressure,left ventricular systolic pressure（LVSP）,left ventricular end diastolic pressure（LVEDP）,LV＋dp/dtmax and LV-dp/dtmax.After that hearts were rapidly excised and weighed.Myocardial infarct size was determined by triphenyltetrazolium chloride（TTC） staining method.Isolated thoracic artery ring preparations were studied in a wire-myograph.The arterial constrictive responses to KCl,CaCl2,phenylephrine（PE）,and caffeine and the arterial diastolic responses to acetylcholine（ACh） were recorded by the Multi Myograph System.To explore the possible mechanism,nitric oxide synthase（NOS） inhibitor N-nitrl-L-arginine methylester（L-NAME） and non-selective cyclooxygenase（COX） inhibitor indomethacin（Indo） were used.The results obtained were as follows：（1） CHF group showed an increased contraction response to KCl（5-100 mmol/L） and PE（1×10-8-3×10-4 mol/L）,and a reduced endothelium-dependent relaxation response to ACh（1×10-12-1×10-4 mol/L） compared with those observed in sham group（P0.01,P0.05）;（2） In the presence of L-NAME（1 mmol/L）,the endothelium-dependent cumulative contractions to ACh（1×10-7-1×10-4 mol/L） was significantly enhanced in CHF group（P0.05）,and this effect was reversed by pretreatment with Indo（10 μmol/L）;（3） In CHF group,the vessels incubated with Indo（10 μmol/L） showed an increased vasodilation induced by ACh（1×10-12-1×10-4 mol/L）（P0.05）;（4） In the Ca2＋-free K-H solution,calcium-dependent contraction curves induced by CaCl2（1×10-4-3×10-2 mol/L） in CHF group significantly shifted to the left compared with sham group（P0.05）;while the vascular contraction induced by caffeine（30 mmol/L） had no significant changes.These findings suggest that thoracic arteries of rats with CHF have endothelial dysfunction,and the contribution of endothelial dilation and contraction was significantly altered in CHF rats.The mechanism could be partly associated with the increased endothelium-dependent contracting factors by COX pathway,or the increased extracellular Ca2＋ influx through voltageoperated channels,thus leading to elevated vasoconstriction.