肾上腺素能受体与心肌肥大的研究进展

心肌肥大是一种较缓慢而有力的代偿形式,然而它不是无限度的,心肌肥大最终将引起心室功能异常而导致心力衰竭,这往往是心血管疾病患者的主要死因之一。肾上腺素能受体(adrenergic receptor,AR)是介导儿茶酚胺作用的一类组织受体,研究表明AR与心肌肥大和心力衰竭的发生密切相关。因此,本文就几种AR与心肌肥大近年的研究进展进行综述,以便更好的了解心肌肥大的发生机理。     

Idiopathic myocardial hypertrophy]

Pathoanatomical studies on the hearts of 20 fatal cases of idiopathic myocardial hypertrophy (IMH) were carried out. In all the cases the dilatational form of IMH was found. The utilization of routine histological methods did not reveal any changes specific for the dilatational form of IMH with the exception of uneven hypertrophy of myocardial fibers. In most cases, sclerotic changes in the endocardium and subendocardial parts of the myocardium were observed in the area of the efferent tract of the left ventricle. In the analysis of case histories of the patients dying with IMH noteworthy was a rapid progression of the symptoms of cardiac failure stubborn to treatment as well as ECG signs of significant disorders in rhythm and conductivity. The etiological factors and pathogenetical mechanisms of IMH remain obscure.     

Beta adrenergic and muscarinic receptors in compensatory cardiac hypertrophy of the adult rat

The beta adrenergic (AR) and muscarinic (MR) receptors have been quantitated in parallel, using ¹²⁵I-pindolol and ³H-quinuclidinylbenzilate, in a model of compensatory left ventricular (LV) hypertrophy (LVH), which developed in rats 4–6 weeks after an abdominal aortic stenosis. Since aortic banding resulted in a pronounced LVH of 62%, the results were expressed both in terms of density (fmol/mg protein) and quantity (fmol per LV). In addition, competition curves using either a specific 1-antagonist or isoproterenol or carbachol allowed the determination of the two AR subtypes and of the low and high affinity sites (defined by the inhibitory constant K _i) for both 1AR and MR. In LVH, receptor density decreased for each of total AR, 1AR subtype, high affinity (K _i 6–8nM) 1AR sites (from 26±2 to 19±3 fmol/mg protein, P<0.05), total MR and high affinity (K _i 12 nM) MR sites (from 63±6 to 40±4 fmol/mg protein, P<0.001). The AR and MR densities dropped in parallel so that the MR/AR ratio remained unchanged. In sharp contrast (because the LVs were bigger) the quantities of total AR, 1 AR subtype, 1AR high affinity sites, total MR and MR high affinity sites per LV were unmodified. Thus, in compensatory LVH the total quantity of receptors per LV was unchanged, suggesting that either both synthesis and degradation were augmented in parallel or that during the process of cardiac hypertrophy they are not regulated, i. e., that the genes encoding for the two receptors were not activated, as it has been suggested for other membrane proteins. Assuming that the high affinity sites represent the receptors coupled to the adenylyl cyclase, we also propose that the overall regulatory systems were modified beyond the level of the receptors.     

环状RNA调控心肌肥大的研究进展

心肌肥大是心对额外负荷、节律变化、房室重构和心功能异常的代偿性改变,但如果病因持续存在或未及时消除,最终将演变为慢性心力衰竭.环状RNA是真核细胞内一类高度保守的闭合环状非编码RNA,且具备保守性、广泛性、稳定性和组织特异性,在基因的表达调控中发挥重要作用.circRNA在心肌肥大中发挥重要调控作用,可通过海绵抑制mi...     

肌原纤维调节因子-1在心肌肥大中的作用研究

目的：研究肌原纤维调节因子-1(MR1)在心肌肥大中的变化及其作用。 方法： 选取rMR1 mRNA的3个Stem-loop结构作为靶点，构建RNA干扰载体，对乳鼠心肌细胞进行瞬时转染，通过定量RT-PCR，选定第1靶点进行RNA干扰以封闭MR1基因；采用心肌细胞［3H］-亮氨酸掺入、形态学检测、蛋白质提取、Western blotting技术，检测蛋白合成速率、细胞表面积、rMR1蛋白表达等指标，观察MR1基因沉默对于血管紧张素Ⅱ (angiotensin Ⅱ, AngⅡ)诱导的乳鼠心肌细胞肥大的影响。 结果： AngⅡ组［3H］-亮氨酸掺入较对照组增加24.1%(P<0.01)，其细胞表面积较对照组高65.8%(P<0.01)，rMR-1蛋白表达水平升高；AngⅡ的上述作用可被卡托普利完全消除；MR1基因封闭后，由AngⅡ诱导的［3H］-亮氨酸掺入降低30.2%(P<0.01)，细胞表面积较AngⅡ组降低31.1%(P<0.01)，rMR-1蛋白表达较对照组减少。 结论： AngⅡ诱导的心肌细胞肥大与rMR-1表达上调有关。MR-1可能通过促进心肌收缩蛋白的合成参与心肌肥大的发生。     

Regression of ventricular hypertrophy abolishes cardiocyte vulnerability to acute hypoxia

Left ventricular hypertrophy (LVH) secondary to a pressure overload commonly leads to perfusion abnormalities that may limit oxygen delivery to the myocardium and, therefore, result in cardiocyte intracellular damage. We initiated this study to test the hypothesis that the increased vulnerability of the hypertrophied left ventricle to acute hypoxia is minimized when LVH regresses and maximal coronary flow returns to normal. Six-month-old spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats were divided into control or one of two antihypertensive treatment groups. A 3-month treatment consisted of captopril (75-100 mg/kg) or hydralazine (80-160 mg/L) with hydrochlorothiazide (500 mg/L) added to each therapy. At the conclusion of the treatment period, the rats were administered a 7% O2-93% N2 gas mixture for 20 minutes to induce acute hypoxic stress during which time hemodynamics, blood gases, and pH were monitored. The heart was then rapidly fixed by vascular perfusion and prepared for electron microscopy. Captopril and hydralazine were equally effective in lowering arterial pressure in both strains, but only captopril was efficacious in reducing heart mass. Hypoxia-induced changes in hemodynamics, blood gases, and pH were similar in all of the groups; PO2 was decreased by about 70%. The electron micrographs revealed that the hypertrophied left ventricle consistently showed morphologic evidence of hypoxic damage (as indicated by T-tubular swelling, intracellular edema, and mitochondrial alterations); in contrast hypoxia had little effect on the non-hypertrophied ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)     

雌激素及雌激素受体对高血压心肌肥厚的影响

雌激素通过雌激素受体（estrogen receptor,ER）的介导对心血管系统发挥保护作用。雌激素被动扩散进入细胞后与雌激素受体结合,通过影响肾素血管紧张素系统（RAS）、NO合成、钙离子通道,改善脂质代谢等方面导致高血压心肌肥厚。雌激素受体调节剂（SERMs）如雷洛昔芬等也可以与ER结合,发挥抗心肌肥厚的作用。     

心脏局部肾素—血管紧张素系统在大鼠容量负荷性心肌肥大中的作用

本文采用大鼠腹腔动—静脉瘘(ACF)伴左肾切除模型,研究容量超负荷时,心脏和循环肾素—血管紧张素系统(RAS)的变化及其与心肌肥大的关系。结果发现,ACF伴左肾切除(ACF NT)大鼠,在心肌肥大的同时,左、右心室的血管紧张素Ⅱ(AngⅡ)含量及血管紧张素转换酶(ACE)活性均显著升高,尽管其血浆AngⅠ、Ⅱ和肾素活性都维持在一个较低水平。提示:(1)心脏局部RAS可能在容量负荷性心肌肥大早期起着不容忽视的作用;(2)心肌AngⅡ的升高与心肌ACE活性增高有关;(3)循环RAS在容量负荷性心肌肥大中不起主要作用。     

睾酮对大鼠心肌梗塞后心肌肥大的影响

本文应用立体形态定量技术,观察睾酮(T)对心肌梗塞后心肌肥大的影响。实验分为:假手术组(S组)、心肌梗塞组(MI组)。心肌梗塞后睾酮治疗组(MIT组)。结果证明,与S组相比,MI及MIT组大鼠心肌细胞核密度明显减少,尤其以MIT组变化显著,MIT组平均核长度明显增加;MI组的 dp/dt max明显降低,T值延长,MIT组的上两指标无显著差异。MI后血浆T总浓度与平均每核心肌细胞体积呈显著正相关关系。提示:睾酮确实促进了MI后心肌肥大,从而促进了心功能的恢复。     

神经肽Y在高血压病心肌细胞肥大中的作用

目的：研究神经肽Ｙ（ＮＰＹ）在高血压心肌细胞肥大中的作用。方法：用腹主动脉狭窄和高盐摄入性高血压大鼠模型,测定对照组和高血压组血浆、心肌ＮＰＹ水平和心肌丝裂素活化蛋白激酶（ＭＡＰＫ）活性。结果：高血压大鼠心重、ＮＰＹ水平和心肌ＭＡＰＫ一生均较对照组显著升高。心肌ＭＡＰＫ活性与左心室肥大程度正相关。结论：ＭＡＰＫ系统可能在ＮＰＹ致心肌细胞肥大的信息传导途径中发挥重要的作用。     

丝裂原活化蛋白激酶信号途径在心肌肥厚中的作用进展

Myocardial hypertrophy is an independent risk factor for cardiac events. Mitogen-activated protein kinases(MAPK), including extracellular signal-regulated kinases, C-jun N-terminal kinases and P38-MAPK, are the common intracellular pathway of transducing hypertrophic signs. All three MAPK subfamilies play an important role in development of myocardial hypertrophy.     

Stereology of myocardial hypertrophy induced by physical exercise

Summary Twenty young female Sprague-Dawley rats were randomly assigned to 2 groups. Ten animals served as sedentary controls, the 10 experimental animals were subjected to a training program with gradually increasing intensity of 18 weeks duration on a motor-driven treadmill. The rats were fixed by retrograde vascular perfusion via the abdominal aorta under anesthesia. Two transverse and 2 longitudinal sections per animal were selected at random from the left ventricular papillary muscles for light and electron microscopic stereological investigation. Length density and surface density of myocardial cells and capillaries were estimated with correction for partial anisotropy and curvature by means of the mathematical model of a Dimroth Watson orientation distribution. Left and right ventricular weight increased by 20% in the exercise group (P<0.001), whereas body weight remained unchanged. Physical training led to a significant increase of heart muscle fiber cross-sectional area by 17% (P<0.01). The ultrastructural volumetric composition of the myocardial cell cytoplasm by myofibrils, mitochondria, and sarcoplasmic matrix remained unchanged. Volume density, length density and surface density of capillaries, as well as capillary cross-sectional area and capillary anisotropy parameters were not significantly altered by training. From the data one concludes an increase of the 3-dimensional capillary-fiber ratio by 19% (P<0.001). Thus physical training induces mild absolute biventricular cardiac hypertrophy in young female rats, in which capillary proliferation compensates for the increase of mean oxygen diffusion distance resulting from fiber thickening, by supplying each unit of fiber length by more units of capillary length.     

Role of adrenals on development of pressure-induced myocardial hypertrophy

The effect of coarctation of the abdominal aorta (AC) and of sham operation (SO) on the development of myocardial hypertrophy was studied in three groups of male rats, i.e., a group without treatment prior to AC or SO (untreated), a group with bilateral adrenalectomy (ADX) 5-7 days before AC or SO, and a group in which the adrenal medulla was removed (MDX) 5-7 days before AC or SO. MDX resulted in functional elimination of the adrenal medulla without apparent effect on cortical function. The animals were killed 7-10 days after AC or SO. AC produced carotid blood pressure (CBP) increases of 33, 31, and 25 mmHg in the untreated, ADX, and MDX groups, respectively. Ventricular weight (HW), ventricular RNA concentration, and RNA-to-DNA ratio increased significantly after AC only in the untreated and MDX groups. In the ADX group, hypertension was followed by an increase in HW that could be detected only after normalization for body weight. It is concluded that absence of the adrenal gland significantly reduces the development of pressure-induced myocardial hypertrophy. Apparently, this is due to the absence of the adrenal cortex and not absence of the adrenal medulla.