Contractile properties of skinned preparations from ischaemic canine myocardium and coronary arteries

The influence of prolonged ischaemia on the regulation of contraction in the myocardium and in the smooth muscle of coronary arteries was investigated. Chemically skinned preparations were used which enabled the contraction to be studied with the environment of the contractile filaments controlled. Myocardial ischaemia was produced in anaesthetized adult beagle dogs by occlusion of the left anterior descending artery for 3 h and followed by 30 min reperfusion. Myocardial tissue and segments from coronary arteries were obtained from the ischaemic infarcted wall region (in vivo ischaemic) and compared with control preparations from perfused coronary arteries and from the free wall of the left ventricle. Coronary and myocardial preparations were also obtained from the heart after a 3 h period in vitro under anoxic conditions at 37°C (in vitro ischaemic) simulating a state of extreme ischaemia. Control myocardial fibres were fully relaxed at pCa (-log-[Ca²⁺]) 9 and developed 24±5% (n=7) of maximum force at intermediate calcium concentration (pCa 5.5). In contrast, the in vivo and in vitro ischaemic preparations produced force at pCa 9 (28±13 and 39±8%, respectively, n=5 and 7) and showed an increased force development at pCa 5.5 (53±11 and 75±5%). The in vivo and in vitro ischaemic coronary arteries relaxed more slowly following calcium removal than control vessels. The in vitro ischaemic vascular preparations developed active force at pCa 9 and showed increased levels of myosin light chain phosphorylation and reduced phosphatase activity. This suggests a reduced rate of dephosphorylation as a cause for the changes in contracile behaviour of the smooth muscle. In conclusion, extreme ischaemia in vitro is associated with a loss of calcium regulation and an increased calcium sensitivity of the contractile system in myocardium and changes in the phosphorylation/dephosphorylation reactions of coronary arteries. The changes in myocardium appear to occur also during ischaemia in vivo, and might contribute to contracture development in cells under conditions when adenosine triphosphate synthesis is reestablished after reperfusion.     

Postextrasystolic potentiation does not distinguish ischaemic from stunned myocardium

Myocardial function is impaired by ischaemia, and it remains depressed during reperfusion following short periods of ischaemia (stunned myocardium). We tested whether ischaemic and reperfusion dysfunction, in particular the time course of its recovery, can be distinguished by postextrasystolic potentiation (PESP). In eight open-chest dogs, posterior systolic wall thickening (sonomicrometry) was reduced by graded occlusion of the left circumflex coronary artery (LCX) from 17.4±6.8% (SD) during control conditions to 10.7±1.3% (mild ischaemic dysfunction), 7.2±2.3% (moderate ischaemic dysfunction), 3.6±1.4% (severe ischaemic dysfunction), and -4.4±3.6% (complete coronary occlusion). Extrasystoles with constant prematurity and a fully compensated postextrasystolic interval were induced after at least 4 min steady-state ischaemia. After each ischaemic period full recovery of posterior systolic wall thickening was assured. During 8 h of reperfusion following a 15-min LCX occlusion, extrasystoles were induced when posterior systolic wall thickening was comparable to one degree of the preceding ischaemic dysfunction. The increases in posterior systolic wall thickening induced by PESP were 10.5±5.8% during control conditions, during ischaemia they were 11.5±3.5% (mild dysfunction), 12.3±4.6% (moderate dysfunction), 12.6±4.1% (severe dysfunction) and 10.4±4.4% (complete coronary occlusion), and during reperfusion they were 12.8±8.2% (severe dysfunction), 13.0±9.7% (moderate dysfunction) and 10.7±2.2% (mild dysfunction). These increments in systolic wall thickening as well as those in ejection thickening were not significantly different. PESP can thus not distinguish between ischaemic and reperfusion dysfunction nor between different degrees of myocardial dysfunction.This study was supported by the Deutsche Forschungsge-meinschaft (He 1320/3-2). cand. med. S. Schäfer was involved in some of these experiments and presented part of the data at the 56th Annual Meeting of the Deutsche Gesellschaft für Herz- und Kreislaufforschung in Mannheim (Z Kardiol 79 [Suppl 1]: 24,1990). Part of the data were also presented at the 11th Congress of the European Society of Cardiology in Nice (Eur Heart J 10 [Suppl]: 242, 1989) and at the 73rd Annual Meeting of the Federation of American Societies for Experimental Biology in New Orleans (FASEB J 3: A841, 1989)     

地高辛抗血清对缺氧损伤心肌组织内洋地黄素和心肌细胞膜ATP酶活性的影响

目的:评价地高辛抗血清对抗心肌缺氧损伤的作用与机制。方法: 制备心肌组织缺氧模型,观察不同剂量的地高辛抗血清对缺氧损伤心肌组织内洋地黄素水平和心肌细胞膜ATP酶活性的影响。结果: 缺氧损伤时心肌组织内洋地黄素水平明显高于正常对照组,心肌细胞膜ATP酶活性明显低于正常对照组;地高辛抗血清能明显拮抗缺氧对心肌细胞膜ATP酶活性的抑制作用。结论: 缺氧所致心肌组织内洋地黄素水平升高是缺氧介导心肌损伤的分子生物学基础,地高辛抗血清通过拮抗内洋地黄素的作用,减轻缺氧所致心肌损伤,对缺氧心肌具有保护作用。     

急性冬眠心肌的能量代谢特点

目的：探索冬眠心肌的能量代谢特点。方法：用悬浮人红血球的ＫＨ液灌流大鼠离体等容收缩心脏，建立急性冬眠心肌模型，以心肌三磷酸腺苷、磷酸肌酸、糖原含量，以及心肌摄取乳酸的量作为代谢指标。结果：（１）冬眠３０ｍｉｎ组心肌三磷酸腺苷（ＡＴＰ）、磷酸肌酸及糖原含量均明显低于平衡末组（Ｐ＜００５），心肌由正常情况下摄取乳酸转为释放乳酸（Ｐ＜００５），在冬眠９０ｍｉｎ组，以上指标与冬眠３０ｍｉｎ组无显著差异；（２）再灌注３０ｍｉｎ，心肌磷酸肌酸和糖原含量及心肌摄取乳酸的量与平衡末组相似（Ｐ＞００５），但心肌三磷酸腺苷含量仍较平衡末组为低（Ｐ＜００５）。结论：急性冬眠期间，心肌对氧及代谢底物的供／均需比例在低水平上保持平衡，保证了心肌的存活     

Role of perfusate hydrogen ion activity in kallikrein release from isolated rat kidneys

The present experiments were performed to investigate whether renal kallikrein release by isolated perfused rat kidneys correlates with acid-base-related parameters. Kallikrein excretion per millilitre of glomerular filtrate was inversely correlated with perfusate pH (r = −0.49, P < 0.001) and HCO₃ ⁻ concentration (r = −0.46, P < 0.005). A direct relationship between kallikrein excretion per millilitre of glomerular filtrate and urinary Na⁺/K⁺ ratio was found (r = 0.59, P < 0.001). Some 86% of the variability (F ratio 110, P < 0.00001) of urinary kallikrein activity was attributable to the perfusate pH and the urinary cation ratio. Therefore, urinary kallikrein activity was highly correlated with perfusate H⁺ activity corrected by the urinary Na⁺/K⁺ ratio (r = 0.92, P < 0.0001). Kallikrein secretion into the distal tubular fluid appears to be regulated by blood H⁺ activity, and modulated by factors that affect the distal Na⁺ and K⁺ handling. The HCO3 ⁻ excretion rate was inversely correlated with the urinary kallikrein activity (r = −0.62, P < 0.001). This finding confirms previous data from the author’s laboratory showing a kallikrein involvement in the regulation of HCO₃ ⁻ secretion in rats and rabbits. Kallikrein probably transduces the sensing of interstitial fluid H⁺ activity by the connecting tubule cells into an appropriate translocation of HCO₃ ⁻ or H⁺ to the tubular lumen by the intercalated cells. Received: 24 April 1995/Received after revision: 23 November 1995/Accepted: 8 January 1996     

AgNORs in the myocardium in ischaemic heart disease complicated by heart failure: a postmortem study.

AIM: To evaluate the interphase ribosomal RNA cistron activity of cardiomyocytes in case with ischaemic heart disease complicated by heart failure. METHODS: Nucleoli were investigated in postmortem myocardium samples from 31 cases with ischaemic heart disease (mean (SEM), 57.4 (6.5) years) with or without severe heart failure (18 and 13, respectively) and from eight healthy people who died in accidents (mean (SEM) 25.3 (4.0) years). Myocardium obtained within one hour after death was frozen in liquid nitrogen. Silver staining for nucleolar organiser regions (AgNOR) was performed with a standard procedure and the mean score obtained. On the basis of these data, the average number of AgNORs per nucleus was determined. The Student's t test was used to compare groups. RESULTS: Compared with controls, the mean numbers of AgNORs per nucleus in cardiomyocytes from ischaemic heart disease patients not complicated with severe heart failure were higher (8.0 v 9.9; p < 0.05), but cases with severe heart failure had a progressive decrease in cardiomyocyte AgNORs. A difference in AgNOR numbers between cases with different ischaemic heart disease courses was found when cases with the same New York Heart Association (NYHA) functional stage III of heart failure were studied. CONCLUSIONS: The significant decrease of AgNORs in cardiomyocytes from cases with severe ischaemic heart disease complicated by heart failure seems to be connected with cardiomyocyte adaptation (a variant of hibernation) to a diminished circulation that, hypothetically, may affect the level of ribosomal RNA synthesis.     

急性缺血心肌的血流量再分布

利用放射性生物微球技术,研究了犬在急性心肌缺血时,侧支循环血流量的再分布,在结扎左前降支冠脉后,中心缺血区血流量明显减少。近边缘区血流量大于中心缺血区血流量,小于远边缘区和非缺血区的血流量。中心缺血区和近边缘区的心内膜下层心肌血流量低于心外膜下层心肌血流量,两者之比小于1.00。随着缺血时间的延长(1—6小时),中心缺血区血流量逐渐减小,而非缺血区的血流量逐渐增加。     

Structural and enzymatic properties of cardiac myosin in ischaemic and non-ischaemic regions of the rat myocardium

Summary In rats with ligation of the left coronary artery changes in ATPase activity and structure of cardiac myosin in both ischaemic and non-ischaemic zones of the myocardium were followed. In control aninals. ATPase activity and the structure of the myosin molecule in right and left ventricles did not differ. Non-specific factors, such as anaesthesia and thoracotomy, can result in a decrease or an increase in ATPase activity respectively.One hour after ligation of the left coronary artery ATPase activity increased in the right, non-ischaemic myocardium and there was a significant right-to-left difference. Four hours after ligation, ATPase activity in both ventricles significantly decreased and the right-left difference disappeared. Within 48 h, normal values were found only in the non-ischaemic right ventricle.Ligation of the left coronary artery results after 48 h in the formation of structural alterations in cardiac myosin, primarily in the left, ischaemic myocardium. These changes are characterised by the formation of myosin aggregates, which have a significantly lower ATPase activity in comparison with monomeric myosin.     

丹参对急性心肌缺血时脂质过氧化的影响

本实验以结扎家兔冠脉左室支造成在体急性心肌缺血模型,以硫代巴比妥酸荧光法测定心肌组织脂质过氧化物含量,探讨心肌脂质过氧化情况及其与心电图ST段改变的关系,并以丹参注射液为心肌保护因素,观察脂质过氧化物、心电图ST段的变化,探讨丹参对心肌的保护作用。实验结果表明:结扎冠脉左室支40分钟时,缺血区心肌脂质过氧化物含量比对照组增加2.4倍(P<0.01),缺血区脂质过氧化物含量与心电图ST段抬高程度呈正相关(r=0.822,P<0.025)。预先静脉注射丹参注射液,使缺血区心肌脂质过氧化物含量较缺血组缺血区降低47.9%(P<0.02).并使冠脉左室支结扎后2至5分钟的心电图ST段抬高程度降低44.8～47.0%(P<0.05)。     

四逆汤抗犬急性心肌缺血的实验研究

目的：观察四逆汤对急性心肌缺血犬心内膜心电图及心肌酶学脂质过氧化损伤等指标的影响。方法：应用结扎犬冠状动脉的方法造成急性缺血模型,描记心电图,检测磷酸肌酸激酶（ＣＰＫ）,磷酸肌酸激酶同功酶（ＣＰＫ－ＭＢ）,谷丙转氨酶（ＡＬＴ）,乳酸脱氢酶（ＬＤＨ）,超氧化物歧化酶（ＳＯＤ）、丙二醛（ＭＤＡ）等指标。结果：四逆汤能显著降低急性心肌缺血犬 心电图缺血范围和缺血程度,降低血ＣＰＫ,ＣＰＫ－ＭＢ,ＬＤＨ等     

Evidence for a link between mechanical and electrical alternans in acutely ischaemic myocardium of anaesthetized dogs

In order to examine the relation between mechanical alternans and associated electrical alternans during acute myocardial ischaemia, we determined the effect of a ventricular premature beat and calcium antagonists on mechanical and electrical alternans during acute coronary occlusion in anaesthetized dogs. Isometric contractions and unipolar electrocardiograms were recorded from ischaemic myocardium. During coronary occlusion, mechanical alternans was accompanied by electrical alternans, which was an alternate change in the ST segment elevation, i.e. the higher ST and the lower ST. Electrical alternans was frequently discordant and in some cases accompanied by discordant mechanical alternans. Both discordant electrical and mechanical alternans became concordant and were potentiated after the ventricular premature beat. In all cases, concordant mechanical alternans was accompanied by concordant electrical alternans and vice versa. In this situation, the higher and the lower ST corresponded to the larger and the smaller contractions respectively. Thus, a fixed correspondence was observed between mechanical and electrical alternans. A fixed correspondence was also observed between mechanical alternans and the variation in the time taken for repolarization of the monophasic action potential. Verapamil and diltiazem inhibited both electrical and mechanical alternans. The present results support the idea that a common mechanism, such as a beat-to-beat cycle of the transmembrane and intracellular movement of calcium ions, may play a role in the mechanisms of electrical and mechanical alternans.     

急性心肌缺血再灌注损伤及其保护的研究：丹参制剂的作用

本文实验材料为家兔心肌,用高效液相色谱法测定腺苷酸类,用分光光度法测定脂质过氧化物和用原子吸收光谱法测定钙的含量。研究表明缺血再灌组ATP、ADP、AMP、AN(腺苷酸总量)、ATP/ADP、ATP/AMP和能荷均比缺血组(Ⅰ)丹参保护组(D)的非缺血区与缺血区中上述指标水平明显降低(P<0.001或P<0.01),与Ⅰ组和D组的非缺血区与缺血区比较,缺血再灌组的缺血区脂质过氧化物水平明显增加(P<0.001)。而该组缺血区心肌钙亦明显增加(P<0.001)。本文研究结果进一步证明丹参可以保护缺血再灌损伤的心肌。     

Effect of anticoagulation upon nephron obstruction in experimental acute ischaemic renal failure. A morphological study

Ischaemic-reperfusion injury as a model of acute renal failure (ARF) results in increased macromolecular permeability, tubular obstruction, and renal oedema. To investigate the role for coagulation in this model, anticoagulated and saline-pretreated rats were subjected to 60 min unilateral renal artery occlusion (RAO). After 15 min of reflow, specimens were collected for electron and light microscopic examination. Morphometry was employed to study podocyte changes and Bowman's space dilatation as measures of increased permeability and tubular obstruction, respectively. After 15 min of reflow, Bowman's space increased significantly and the podocytes were markedly widened and flattened. Rats pretreated with heparin or warfarin showed less widening of Bowman's space than saline-treated rats, whereas no significant difference was seen regarding the podocyte changes. In saline-treated rats, fibrin-positive material was seen in the tubules but not in the urine sediments collected after 90 min of reflow, either due to fibrinolysis or poor urinary elimination. The results suggest that anticoagulation does not preclude the glomerular sieving of macromolecules, but seems to reduce tubular obstruction, probably by preventing conversion of filtered fibrinogen into fibrin.     

Serum amyloid A concentrations during the course of acute ischaemic heart disease.

Serum amyloid A concentrations were determined in serial serum samples of 41 patients with confirmed acute myocardial infarction (10 with acute ischaemia and two with myocarditis). A sharp increase in serum amyloid A concentration was observed early at onset of infarct; it peaked on the third day (up to 2200 fold of normal values) and declined towards normal during the following days, if no complications occurred. Different patterns were observed in patients with acute ischaemia or myocarditis. Although serum amyloid A is not a specific marker, it may, because of its high sensitivity and characteristic patterns of change, represent an additional useful biochemical variable in the diagnosis, follow up, and prognosis of acute ischaemic heart disease.     

Re-expression of nestin in the myocardium of postinfarcted patients

Intact cardiac muscle cells in the adult heart do not express intermediate filament nestin. In this study, we report on widespread expression of intermediate filament nestin in human myocardium of patients who died from the myocardial infarction. Nestin was detected in cardiomyocytes, endothelial cells, and few interstitial cells. Elevated levels of nestin were observed in cardiac muscle cells in all specimens, although the intensity of immunoreactivity and distribution of the signal differed. The strongest immunoreactivity was observed from 4 days after myocardial infarction in the infarction border zone where nestin was distributed homogeneously in the entire sarcoplasm of cardiac muscle cells. Within the following week, nestin in immunoreactive cardiomyocytes was redistributed and restricted to small subsarcolemmal foci and to intercalated discs. Angiogenic capillaries that grew between vital nestin-positive cardiomyocytes and entered the necrotic area expressed also high levels of nestin. Nestin-positive endothelial cells were often observed in mutual interactions with nestin-positive cardiac muscle cells. These findings document a crucial role of nestin in remodeling cytoskeleton of cells in the human postinfarcted myocardium.     

Experimental investigations on estimation of myocardium and adipose tissue composition of human heart. A critical review (author's transl)]

Only quantitative assessment of the active mass of heart muscle gives correct information about the functional capacity of the human heart and is essential for discussion of pathological conditions.Removal of adipose tissue from the heart, a method created by Müller, does not yield correct results because complete separation of adipose tissue from the fibres of the myocardium is difficult.Masshoff and Scheidt have produced a method which allows estimation of active parenchyma of the human heart without removing adipose tissue. This method is based on the physical principle for binary mixtures expressing that qualities of bicomponent mixtures can be derived from the qualities of the individual components by consideration of different quantitiesUsing this method myocardium is considered as a mixture of two solid masses, namely myocardium and adipose tissue. According to Masshoff and Scheidt values of constant densities are used which represent mean values out of a large number of single values.Thus, this method is exclusively based on the assessment of weight and density of total heart by the use of a pyknometer.The following experiments were carried out for the purpose of checking this method with regard to its reliability.     

Effect of a new nitric oxide donor on the biomechanical performance of the isolated ischaemic rat heart

The effect of a new nitric oxide (NO) donor, a meso-ionic 3-aryl substituted oxatriazole-5-imine derivative, GEA 3162 was studied on constant flow-perfused ischaemic Langendorff rat heart. The perfusion was kept constant at a rate of 16 mL min^?1. Ischaemia was induced by a low flow rate of 0.8 mL min^?1 for 30 min, and was followed by a 40-minute reperfusion. In the first set of experiments the effects of GEA 3162-infusion were examined on perfusion pressure, left ventricular pressure, heart rate and left ventricular dP/dt. GEA 3162 infusion did not affect the pre-ischaemic maximum of left ventricular pressure. During reperfusion, maximal left ventricular pressure, maximal and minimal dP/dt values in the GEA 3162-treated group significantly exceeded those of the untreated controls (by 19.3, 36.0 and 18.0%, respectively). During reperfusion, perfusion pressure increased continuously in the control group indicating an increasing coronary resistance, but it was kept at a continuous low level with GEA 3162 treatment. In a second set of experiments bradykinin was infused in order to test the endothelial function before ischaemia and during late reperfusion. Bradykinin elicited significant vasodilation in the control group during reperfusion, meanwhile it did not cause further change in coronary resistance in the GEA 3162-infused group. We suggest, that GEA 3162 may have a protective effect on isolated rat heart in ischaemia and reperfusion, that results in an improved cardiac performance compared with untreated hearts.     

Postmortem ion analysis of the myocardium in surgically correctible heart malformations

Commonly, children dying after operation on congenital cardiac malformation, show only minor histological changes in the myocardium. We have attempted to correlate the myocardial ion (Na+, K+, Ca2+) composition with the probable severity of hypoxia. Mean Ca2+ content has been plotted against the mean Na+/K+ ratio of every heart in the present study. A good correlation between these two parameters was demonstrated with full separation of controls and hearts with congenital malformations.     

慢性心衰大鼠心脏CGRP免疫阳性细胞的形态与分布

目的研究慢性心衰(CHF)大鼠心脏降钙素基因相关肽(CGRP)免疫阳性细胞的分布变化规律。方法以阿霉素(ADR)制备慢性心衰模型,采用免疫组织化学方法结合医学图像分析系统对CHF大鼠心脏CGRP免疫阳性细胞的形态分布变化进行观察。结果显示正常组CGRP免疫阳性细胞主要以圆形和椭圆形为主,CHF组细胞以指环形为主;CHF时CGRP免疫阳性细胞的数密度和面密度明显降低(P<0.05)。结论CHF时CGRP免疫阳性细胞形态和数量与正常时相比,均有明显变化,与CHF的发生、发展密切相关。