Effect of phentolamine on myocardial extracellular matrix of cardiac remodeling in rats

Objective:To study the effects of phentolamine on myocardial extracellular matrix of cardiac remodeling induced by norepinephrine in rats.Methods:24 SD rats were divided into 3 groups randomly:control groups,norepinephrine groups(model groups),norepinephrine +phentolamine groups(treatment groups).Echocardiography was used to detect changes in cardiac structure and function,the level of collagen volume fraction(CVF) and hydroxy-proline as well as collagen content were determined in myocardial tissue,matrix metalloproteinases-2 and collagen Ⅰin myocardial tissue were localized by immunohistochemitry.Results:Compared with control groups,left ventricular hypertrophy in the model group rats,the livdioxyproline content and CVF was significantly higher(P0.01),and matrix metalloproteinase- 2 and collagen Ⅰ protein expression was significantly increased(P0.01).Phentolamine significantly improved cardiac hypertrophy in treatment group rats,reduced hydroxy-proline,CVF,matrix metalloproteinase 2and collagen Ⅰ protein expression(P0.05).Conclusions:Phentolamine can effectively reduce the incidence of myocardial hypertrophy and myocardial extracellular matrix remodeling in SD rats,and it can ease myocardial extracellular matrix of cardiac remodeling.It may he associated with reduced expression of matrix metalloproteinase 2 and collagen Ⅰ in myocardial tissue remodeling.     

氧化应激对心房颤动心房间质纤维化影响的实验研究

Objective The aim of the present study was to determine the effects of probucol on oxidative stress in atrial interstitial fibrosis of long-term rapid pace-induced atrial fibrillation(AF). Methods In this study, twenty dogs were randomly divided into 3 groups, sham-operated group ( n = 6 ), control group ( n = 7 ) and probucol group( n =7). One thin silicon plaque containing 4 pairs of electrodes were sutured to right atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial pacing until pacing stop. Before and after 6-week rapid atrial pacing, transthoracic and transoesophageal echocardiographic examinations were performed The following data were collected including left atrium(LA) maximal volume( LAVmax), LA minimal volume ( LAVmin), LA ejection fraction ( LAEF), left atrial appendage (LAA) maximal volume (LAAVmax), LAA minimal volume ( LAAVmin ), LAA ejection fraction (LAAEF), LAA maximal forward flow velocity( V-LAA+ )and LAA minimal backward flow velocity( V-LAA- ). We attempted to identify collagen volume fraction(CVF) by Masson staining. The expression of metal metalloproteinase-9( MMP-9 ) and issue inhibitor of metalloproteinase-1 ( TIMP-1 ) was examined using western blot. The index of oxidative stress was measured by color comparison. Results ( 1 ) After 6-week atrial tachypacing,the LA and LAA volumes increased significantly, LAEF, LAAEF, V-LAA + and V-LAA- decreased dramaticaly in the control group dogs. Compared with the control group, the LA and LAA volumes were significantly smaller, LAEF, LAAEF,V-LAA + and V-LAA-were dramaticaly higher in probucol group. (2) Compared with the sham-operated group,the index of oxidative stress was increased dramatically in the control group dogs. The index of oxidative stress in probucol group was lower than the level in control group. Probucol could reduce the inducibility and duration of AF and prevent the pathohistological and ultrastructural changes in atria induced by chronic rapid atrial pacing. (3) Compared with the sham-operated group, the CVF was dramatically increased in left and right atrium of control group (P ＜ 0. 01, respectively). (4) Compared with the sham-operated group, the expression of MMP-9 was increased significantly,while the expression of TIMP-1 decreased dramatically in control group. Probucol can reduce the protein expression of MMP-9 and increase the expression of TIMP-1. ( 5 ) MDA was correlated positively with the CVF of atrial myocytes ( r = 0. 976, P ＜ 0. 001 ). Conclusions As an antioxidant, probucol can prevent atrium CVF of AF in chronic rapid atrial pacing dogs. There may be a relationship between oxidative stress and atrial interstitial fibrosis of AF.     

氧化应激对心房颤动心房间质纤维化影响的实验研究

Objective The aim of the present study was to determine the effects of probucol on oxidative stress in atrial interstitial fibrosis of long-term rapid pace-induced atrial fibrillation(AF). Methods In this study, twenty dogs were randomly divided into 3 groups, sham-operated group ( n = 6 ), control group ( n = 7 ) and probucol group( n =7). One thin silicon plaque containing 4 pairs of electrodes were sutured to right atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial pacing until pacing stop. Before and after 6-week rapid atrial pacing, transthoracic and transoesophageal echocardiographic examinations were performed The following data were collected including left atrium(LA) maximal volume( LAVmax), LA minimal volume ( LAVmin), LA ejection fraction ( LAEF), left atrial appendage (LAA) maximal volume (LAAVmax), LAA minimal volume ( LAAVmin ), LAA ejection fraction (LAAEF), LAA maximal forward flow velocity( V-LAA+ )and LAA minimal backward flow velocity( V-LAA- ). We attempted to identify collagen volume fraction(CVF) by Masson staining. The expression of metal metalloproteinase-9( MMP-9 ) and issue inhibitor of metalloproteinase-1 ( TIMP-1 ) was examined using western blot. The index of oxidative stress was measured by color comparison. Results ( 1 ) After 6-week atrial tachypacing,the LA and LAA volumes increased significantly, LAEF, LAAEF, V-LAA + and V-LAA- decreased dramaticaly in the control group dogs. Compared with the control group, the LA and LAA volumes were significantly smaller, LAEF, LAAEF,V-LAA + and V-LAA-were dramaticaly higher in probucol group. (2) Compared with the sham-operated group,the index of oxidative stress was increased dramatically in the control group dogs. The index of oxidative stress in probucol group was lower than the level in control group. Probucol could reduce the inducibility and duration of AF and prevent the pathohistological and ultrastructural changes in atria induced by chronic rapid atrial pacing. (3) Compared with the sham-operated group, the CVF was dramatically increased in left and right atrium of control group (P ＜ 0. 01, respectively). (4) Compared with the sham-operated group, the expression of MMP-9 was increased significantly,while the expression of TIMP-1 decreased dramatically in control group. Probucol can reduce the protein expression of MMP-9 and increase the expression of TIMP-1. ( 5 ) MDA was correlated positively with the CVF of atrial myocytes ( r = 0. 976, P ＜ 0. 001 ). Conclusions As an antioxidant, probucol can prevent atrium CVF of AF in chronic rapid atrial pacing dogs. There may be a relationship between oxidative stress and atrial interstitial fibrosis of AF.     

Effect and mechanism of Irbesartan on occurrence of ventricular arrhythmias in rats with myocardial ischemia through connexin43(cx43)

Objective: To explore the effect and mechanism of angiotensin Ⅱ receptor blockers-Irbesartan on occurrence of ventricular arrhythmias in rats with myocardial ischemia. Methods: Rats with embryonic cardiomyocytes-H9c2 were randomly divided into control group, ischemia group, Irbesartan group and Irbesartan+ischemia group. The cell viability of rats in each group was tested using MTT. Real-time PCR was employed to detect the expression of connexin43(Cx43) mR NA and western blot to detect the expression of Cx43 and phosphorylated Cx43. SD rats were randomly divided into the sham-operation group(SO), myocardial infarction group(MI), Irbesartan group and MI+ Irbesartan group, with 10 rats in each group. HE staining was employed to observe the change in the pathomorphology of left ventricular tissue and TUNEL method to analyze the cell apoptosis in the tissue. The immunofluorescence was adopted to observe the expression and distribution of Cx43 in the left ventricular myocardium and study the change in the expression of Cx43 in the cardiac muscular tissue at mR NA and protein level. Results: The intervention of Irbesartan in the condition of ischemia indicated the significant decrease in the number of necrotic cells. The expression of Cx43 was significantly decreased under the culture of ischemia(P0.05), but in the presence of Irbesartan, the expression of Cx43 was increased compared with the ischemia group(P0.01). The results of WB assay showed the similar trend of change at mRNA level. There was the significant difference in the score of ventricular arerythmia between MI group and SO group(P0.01). The incidence of ventricular tachycardia or ventricular fibrillation was significantly increased compared with the one in SO group(P0.05). There was the significant difference in the overall score between MI+Irbesartan group and MI group(P0.05). The expression of Cx43 in the cardiac muscular tissue in MI group was significantly decreased(P0.01 vs SO group). But the expression of Cx43 was increased after the treatment with Irbesartan. Conclusions: Irbesartan can inhibit the injury of H9c2 cardiomyocytes and the decreased expression of Cx43 that are induced by the ischemic myocardial infarction. Irbesartan can also improve the reconstruction of Cx43 in rats with ischemic myocardium to inhibit the myocardial infarction-induced arrhythmias.     

Effects of Ang Ⅱ perfusion on transmural heterogeneous of Cx43 in acute myocardial ischemia reperfusion

Objective:To observe the effects of angiotensin Ⅱ(Ang Ⅱ) pefusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion(MIR),and investigate the role of rennin-angiotensin system in malignant ventricular arrhythmia induced by MIR.Methods:Twenty rabbits were randomly divided into MIR group(n=10) and Ang Ⅱ group(n=10).MIR model was produced with traditional ligation and opening of the anterior descending coronary artery in all animal.The hearts in vitro in the MIR group and the Ang Ⅱ group were perfused with simply improved Tyrode's solution and containing Ang Ⅱ Tyrode's solution respectively.90%monophasic action potential repolarization duration,transmural dispersion of repolarization.Cx43 protein(Cx43-pro) and mRNA(Cx43-Cq) expression in subepicardial,midmyocardial and subendocardial myocardium were measured in both groups.The greatest differences of Cx43-pro and Cx43-Cq among three myocardial layers were calculated and shown with △Cx43-pro and △Cx43-Cq respectively.Results:After Ang Ⅱ perfusion,90%monophasic action potential repolarization duration among three myocardial layer were significantly prolonged(P 0.05 and P 0.01),and transmural dispersion of repolarization also significantly increased compared with the MIR group(P 0.05).Compare with the MIR group,three myocardial Cx43-pro and Cx43-Cq expression in the Ang Ⅱ group were significantly decreased(P 0.05 and P 0.01).but△Cx43-pro and △Cx43-Cq were significant increased.Conclusions:Renin-angiotensin system increases transmural heterogeneity of Cx43 expression in the rabbit model with MIR by Ang Ⅱ,and enlarge transmural dispersion of repolarization among three myocardial layers of left ventricular which induces malignant ventricular arrhythmia.     

Long-term effects of simvastatin on protection against atrial fibrillation in patients with acute myocardial infarction

Objective To investigate the impact of simvastatin on blood lipid and the incidence of atrial fibrillation and ischemic-related events in patients with acute myocardial infarction accompanied by paroxysmal atrial fibrillation. Methods One hundred and three patients with acute myocardial infarction and paroxysmal atrial fibrillation were selected as subjects,and were divided into a simvastatin group and a control group. Forty-five patients were in the simvastatin group,who took simvastatin 20mg/d orally for 18 months;fifty-eight patients were in the control group,and received conventional therapy except for statins. All patients were followed up for 18 months. The level of blood lipid,recurrence rate of paroxysmal atrial fibrillation,incidence rate of persistent or permanent atrial fibrillation,and the ischemic-related events were investigated and compared between the two groups. Results ① The levels of blood lipids did not change significantly in the control group(P>0.05) ;concentrations of total cholesterol(TC) and low density lipoprotein cholesterol(LDL-C) decreased significantly after treatment of simvastatin(P<0.05) . ② Recurrence of atrial fibrillation was observed in five patients during 18 months follow-up in the simvastatin group(11.1%) ,whereas it occurred in 14 patients of the control group(24. 1%,P<0.05) ;the occurrence rate of persistent or permanent atrial fibrillation in the simvastatin group was 4.4%,which was lower than that of control(12.1%,P<0.05) . ③ Nine patients had ischemic-related events in the simvastatin group(20.0%) ,with three heart failures(6.6%) ,two rehospitalizations for deterioration of coronary heart diseases(4.4%) ,three cardiac deaths(6.6%) ,and one cerebral stroke(2.2%) ,which was lower evidently than in the control group(41.4%,P<0.05) . Conclusions Simvastatin can not only decrease the levels of serum TC and LDL-C but also prevent the occurrence of atrial fibrillation and ischemic-related events.     

Effect of levocarnitine on TIMP-1,ICAM-1 expression of rats with coronary heart disease and its myocardial protection effect

Objective:To study the effect of levocarnitine(L-CN) on tissue inhibitor of metalloproteinase-1(TIMP-1) and intercellular adhesion molecule-1(ICAM-1) expression of rats with coronary heart disease and evaluate the protective effect of L-CN on myocardial cells.Methods:Highfat diet feeding and intraperitoneal injection of pituitrin was performed on rats in model group and CHD Model of rats was built.Rats with successful model-building were selected and divided into L-CN group and Ctrl group randomly.Rats in L-CN group were given L-CN treatment,with intraperitoneal injection of 200 mg·kg~(-1)?d~(-1) and successive administration for 3 d.Rats in Ctrl group were given equal volumes of normal saline.Blood was collected from carotid artery at different time and expression quantity of creatine kinase-MB(CK-MB) and Troponin Ⅰ(Tn Ⅰ)in serum was detected.Rats in each group were put to death and were separated to obtain the myocardial tissue.Real-time PCR and Western Blotting hybridization were performed to detect the TIMP-1.ICAM-1 expression in myocardial tissue in each group.Statistical analysis was employed to explore the expression changes of TIMP-1 and ICAM-1.and ELISA test was used lo analyse the expression changes of myocardial necrosis marker- CK-MB and Tn I to learn the effect of L-CN and its myocardial protective effect.Results:The total cholesterol,triglyceride and blood glucose levels of rats in model group were significantly higher than that in control group,which indicated that due to high-fat diet feeding,blood lipid of rats in model group was obviously higher than that in control group.In myocardial tissue of rats in model group,TIMP-I level significantly reduced and ICAM-1 level significantly increased(P0.0l).In model group,after L-CN treatment.TTMP-I level had double increase,while ICAM-1 level had 43%of decrease in L-CN group compared with Ctrl group.After L-CN intervention treatment.CK-MB and Tn Ⅰ content in L-CN group relatively reduced compared with Ctrl group.The difference among groups was obvious(P0.01).Condusions:L-CN could increase the TTMP-I expression level and inhibit the ICAM-1 expression level.L-CN has a certain myocardial protective effect     

Effects of AT1 Antagonist on MMP2, MMP9 Expression and Collagen Remodeling in Left Ventricle of Rabbit Undergoing Chronic Pressure Overload

Objectives To study the effects of AT1 antagonist on MMP2, MMP9 expression and collagen remodeling in left ventricle of rabbit undergoing chronic pressure overload. Methods 30 rabbits were randomly divided into 3 groups (n= 10,each group), including sham operation group, abdominal aorta banded group(banded group), abdominal aorta banded valsartan group (valsartan group).Twelve weeks after operation,hemodynamic parame-ters were acquired, then collagen volume fraction(CVF) and MMP2, MMP9 expression of left ventricle were measured by using VG and immunohistochemical stain. Results Compared with sham operation group, both MMP2 and MMP9 expression were enhanced in banded group; meanwhile, LVW/BW,LVEDP and CVF increased significantly. Compared with banded group, both MMP2 and MMP9 expression were weakened in valarstan group; simultaneously,LVW/BW, LVEDP and CVF decreased significantly.Conclusions Expression of MMP2 and MMP9 was enhanced in left ventricle of rabbit undergoing chronic pressure overload, which may be associated with collagen proliferation, ventricule remodeling and impaired heart function; Valsartan could inhibit collagen proliferation, prevent ventricule remodeling and preserve heart function by inhibiting abnormal expression of MMP2 and MMP9.     

Mechanism of TLR-4/NF-κB pathway in myocardial ischemia reperfusion injury of mouse

Objective: To detect the expression of Toll-like receptor 4(TLR-4) and NF-κB and to discuss the mechanism of TLR-4/NF-κB pathway in the myocardial ischemia reperfusion injury of mouse. Methods: TLR-4 mutant mice and wild homozygous mice were divided into the model group and sham group. Mice in the model group were given the ligation of left anterior descending coronary artery for the modeling, while mice in the sham group were not given the ligation after threading. The cardiac muscle tissues were collected for the morphological observation. The immuno histochemistry was employed to detect the expression of NF-κB, Western blot was used to detect the expression of TLR-4 and ELISA to detect the expression of serum inflammatory factors. Results: The expression of NF-κB in TLR-4 null mice after the myocardial ischemia reperfusion was significantly lower than that in wild homozygous mice. For the model group and sham group, the expression of TLR-4 in wild homozygous mice was all significantly higher than that in TLR-4 null mice, while the expression of TLR-4 in TLR-4 null mice in the model group was significantly higher than that in sham group, with the statistical difference(P0.05). The expression of inflammatory factors in TLR-4 null mice and wild homozygous mice in the model group was significantly higher than that in sham group. The expression of all factors in group A with TLR-4 null was significantly lower than that in group B with wild homozygous type, with the statistical difference(P0.05). Conclusions: TLR-4/NF-κB pathway is closely related to the myocardial ischemia reperfusion injury, which plays its role through the release of inflammatory cytokines.     

快速右心房起搏对实验犬心房胶原纤维分布的影响

目的 实验探讨切除上腔静脉中部和主动脉根部脂肪垫(简称脂肪垫)对快速右心房(RA)起搏实验犬的心房胶原容积分数(CVF)的空间分布变化意义.方法 24只成年健康杂种犬雌雄不限,随机分为切除脂肪垫组、保留脂肪垫组和假手术组,每组8只.RA心外膜起搏6周,按左心房(LA)、RA、左心耳(LAA)、右心耳(RAA)、房间隔(AS)5个部位取材,Masson染色测算CVF,荧光定量聚合酶链反应技术检测缝隙连接蛋白(Cx)40和Cx43mRNA表达.结果 (1)假手术组和切除脂肪垫组CVF在部位分布上差异无统计学意义;保留脂肪垫组胶原增生明显,见于LAA和AS,P＜0.01.(2)假手术组Cx40mRNA含量分布在LA、RA、RAA、AS间差异无统计学意义;Cx40mRNA表达在切除脂肪垫组与保留脂肪垫组以LA、LAA增多且组间差异有统计学意义(P＜0.01).(3)假手术组Cx43mRNA含量优势表达于RA、RAA,P＜0.01;而在切除脂肪垫组LA、RA、RAA、AS其含量增多,在保留脂肪垫组的相应部位,其含量减少,P＜0.01.结论 快速RA起搏所致心房间质纤维增生具有空间各异向性,去迷走神经能抑制此效应.迷走神经效应影响起搏后Cx40mRNA与Cx43mRNA在心房与心耳间含量的表达.     

持续快速心房起搏对犬肺静脉及心房组织连接蛋白43和Ⅲ型胶原的影响

目的　探讨持续快速心房起搏对犬肺静脉和心房组织连接蛋白 43(Cx43)和Ⅲ型胶原的影响。方法　16只杂种犬,随机分为持续快速心房起搏组(8只)和正常对照组 (8只 ),前者以 400次 /min的频率持续起搏 10周,建立心房颤动(房颤)动物模型。分别取两组犬的左上肺静脉、左房游离壁和右心耳等部位的心肌组织进行Cx43的免疫荧光半定量分析和Ⅲ型胶原纤维定量分析。结果10周后快速心房起搏组所有犬均可诱发出持续性房颤。快速心房起搏组犬肺静脉、左房游离壁和右心耳部位的Cx43水平显著高于正常对照组犬各相应的部位 (肺静脉: 3370 .91±275. 11与1405 .82±90. 38, P<0. 05;左房游离壁: 2448. 68±272 .10与 1467. 12±147 .93,P<0. 05;右心耳: 2331 .96±199 .61与 1288. 27±216 .22, P<0 .05)。快速心房起搏组犬肺静脉Cx43的水平显著高于左心房游离壁和右心耳(P<0. 05),而左心房和右心耳部位的Cx43水平差异无统计学意义 (P>0. 05)。持续快速心房起搏组犬肺静脉、左房游离壁和右心耳等部位的Ⅲ型胶原含量显著高于正常对照组犬各相应部位(肺静脉: 3301 97±309 70与 1404 56±178 02, P<0 05;左房游离壁: 2477 86±190. 43与1479. 20±187 .17, P<0 .05;右心耳: 2045 .92±139 .43与 1417. 07±139. 43,P<0 .05 )     

交感神经刺激对大鼠缺血性室性心律失常的影响及其机制的探讨

目的 探讨大鼠急性心肌缺血时交感神经刺激对室性心律失常的影响及其潜在的机制.方法 结扎大鼠冠状动脉前降支制备急性心肌缺血模型后随机分组作为心肌缺血组(MI组,n=25)、缺血+交感神经刺激组(MI-SS组,n=25)、交感神经刺激+酚妥拉明+缺血组(MI-SS-Phen组,n=15)、交感神经刺激+普萘洛尔+缺血组(MI-SS-Prop组,n=15)和假手术组(SO组,n=20).心电图监测室性心律失常的发生.蛋白免疫印记法(Western blot)检测缝隙连接蛋白43(Cx43)的磷酸化蛋白及总量表达变化.逆转录聚合酶链反应(PCR)分析Cx43 mRNA的表达变化.免疫荧光观察Cx43表达分布情况.结果 结扎冠状动脉30 min内MI、MI-SS和MI-SS-Phen组分别有1、3和2只大鼠死于心室颤动(室颤);MI-SS组室性心动过速(室速)/室颤发生率(80.0%,20/25)较MI组(52.0%,13/25)明显增加(P＜0.05);与MI-SS组相比,普萘洛尔明显阻断了交感神经刺激促室速/室颤发生的作用(13.3%,2/15,P＜0.05).冠状动脉结扎30 min后,MI组磷酸化Cx43的比例较SO组显著降低(P＜0.05),但其总量并未减少(P＞0.05).与MI组相比,MI-SS组磷酸化Cx43的比例明显增加(P＜0.05),同时其蛋白总量的表达显著降低(P＜0.05);普萘洛尔显著抑制了交感神经刺激导致的Cx43蛋白降解的作用,同时抑制了缺血引起的Cx43脱磷酸化(P＜0.05).MI和MI-SS组Cx43mRNA表达均较SO组显著减少(P＜0.05).免疫荧光结果 显示,与SO组相比,MI组Cx43由端-端连接转化为侧-侧连接,而MI-SS组Cx43分布明显紊乱,不能分辨出Cx43的分布模式.结论 交感神经刺激能够促进室性心律失常的发生,可能主要与β肾上腺素受体的激活从而促进了Cx43的降解有关.     

Remodeling of myocardial sleeve and gap junctions in canine superior vena cava after rapid pacing

Objective We studied the response of the superior vena cava (SVC) myocardial sleeve to atrial fibrillation (AF). Methods and results We examined adult male dogs without pacing (N=6) and after rapid atrial pacing (600 bpm) for 2 weeks (P2w; N=5) and 6–8 weeks (P6–8w; N=5). After pacing, the sleeve was increased in thickness (non-paced vs. either paced group, both P<0.05). This was associated with an increase in proliferative activity, which was higher in the P2w than the P6–8w animals (P < 0.05). In addition, collagen content increased, and the component cardiomyocytes become more unevenly oriented and shorter and narrower in shape (non-paced vs. either paced group, both P < 0.05). Pacing had different effects on connexin40 (Cx40) and Cx43 gap junctions. There was a 98% increase in Cx43 signal in P2w, and a 74% increase in P6–8w animals (non-paced vs. each paced group, both P < 0.05). In contrast, Cx40 signal decreased 47% in P2w but increased 44% in P6–8w animals (non-paced vs. each paced group, both P < 0.05). Conclusions Rapid atrial pacing results in a specific pattern of remodeling of the canine SVC sleeve, including changes in size and shape, spatial orientation, and gap junction expression profile of the component cardiomyocytes. These changes may co-operatively affect the electrical properties and contribute to the formation and maintenance of the arrhythmogenic substrate of AF.     

Tissue structure and connexin expression of canine pulmonary veins

OBJECTIVE: Rapid electrical activity in pulmonary veins (PVs) has been proposed as a mechanism for focal atrial fibrillation. The way in which the myocardial sleeve inside PVs can form a substrate for focal activity is not well understood. Therefore, we have studied tissue structure and connexin distribution at the veno-atrial transition in the dog. METHODS: In adult mongrel dogs, the anatomy of the PV area was studied. Tissue structure in individual veins was assessed in formalin fixed sections using Masson's Trichrome staining. Gap junction protein distribution was examined using antibodies against connexin40 (Cx40) and connexin43 (Cx43). The ultrastructure of myocytes in myocardial sleeves was studied using electron microscopy. RESULTS: Individual PVs in the dog had a gross morphology similar to that observed in the human, with myocardial sleeves extending into the veins for 4-20 mm. In all veins examined, myocytes in myocardial sleeves had a normal atrial morphology and anti-desmin staining pattern. Cx43 was expressed throughout the sleeve at levels comparable to normal atrial myocardium. By contrast, Cx40 expression was lower in myocardial sleeves than in the rest of the left atrium. Myocytes in the sleeve, which were ultrastructurally similar to normal atrial myocytes, were predominantly organized in a circumferential pattern. CONCLUSIONS: PVs in the dog and various canine models of heart disease will be a suitable model for (patho)physiology of the veno-atrial transition. Myocytes in myocardial sleeves are similar to normal atrial myocytes. The circumferential orientation of these myocytes may provide a substrate for rapid circular reentry.     

Altered Pattern of Connexin40 Distribution in Persistent Atrial Fibrillation in the Goat

Cx40 Distribution in Goat Atrial Fibrillation. Introduction : Since altered expression of gap junction proteins (connexins) in diseased myocardial tissue may lead to abnormal electrical coupling between cardiomyocytes and hence contribute to arrhythmogenesis, the expression of connexin(Cx)40 and Cx43 was studied in atrial appendage from goats in sinus rhythm (SR) and persistent atrial fibrillation (AF).
Methods and Results : Biopsies were taken from the left and right atrial appendages from goats in SR or after pacing-induced persistent AF. Analyses of Cx40 and Cx43 mRNA and protein levels, using quantitative (competitive) polymerase chain reaction and western blotting, respectively, revealed no significant changes in the overall expression of Cx40 and Cx43 as a result of persistent AF. At the cellular level, immunohistochemistry and confocal laser canning microscopy showed a homogeneous distribution of either connexin in atrial sections taken during SR. After induction of AF, the distribution of Cx43 gap Junctions was unchanged whereas the Cx40 pattern showed marked inhomogeneities with small areas (0.15 to 0.6 mm in diameter, 25% of section surface area) of low-density Cx40 located between larger areas of normal (unchanged) Cx40 density. Activation mapping (244 electrodes, spatial resolution 2.25 mm) of the right atrial wall did not reveal changes in atrial conduction velocity.
Conclusion : Pacing-induced persistent AF in the goat gave rise to changes in the spatial organization of Cx40 gap junctions. Although the overall conduction velocity appeared not to have changed, microheterogeneities in conduction due to the local redistribution of Cx40 gap junctions might have contributed to the initiation and maintenance of AF.     

急性心房颤动缝隙连接蛋白40和43重构及蝙蝠葛碱的干预作用

采用快速心房起搏致家兔急性心房颤动 (简称房颤 )模型 ,观察心房肌缝隙连接蛋白 4 0和 4 3(Cx4 0、Cx4 3)含量和分布的改变以及钙通道阻滞剂蝙蝠葛碱干预的防治效果。 36只家兔随机等分为 3组 :对照组、房颤组和蝙蝠葛碱组。经颈内静脉将电极置入右房 ,对照组不予快速心房起搏 ,另两组以 6 0 0次 /分行快速起搏以诱发房颤。蝙蝠葛碱组于快速起搏前 30min按 5mg /kg静脉注射进行干预 ,另两组给予等容量的生理盐水。连续刺激并且房颤 8h后 ,开胸取右心耳组织 ,用Westernblot检测Cx4 0和Cx4 3的含量 ,用免疫荧光抗体标记激光共聚焦显微镜检测Cx4 0和Cx4 3的分布。结果 :房颤组心房肌组织Cx4 0和Cx4 3含量较对照组降低 (P均 <0 .0 1) ,端端分布减少 ,侧侧分布相对增加 ,以细胞间端端连接减少为主 ,二者均呈现不均一分布。蝙蝠葛碱组Cx4 0和Cx4 3的含量较对照组降低但差异无显著性 (P均 >0 .0 5 ) ,较房颤组升高且差异有显著性 (P均 <0 .0 5 ) ,二者分布不均一程度较房颤组减轻。结论 :快速心房起搏致急性房颤可引起缝隙连接蛋白 4 0和 4 3重构 ,快速起搏前用蝙蝠葛碱干预能有效减轻急性房颤时的缝隙连接蛋白重构。     

缝隙连接蛋白43在老年大鼠缺血性室性心律失常中的作用

目的 探讨缝隙连接蛋白43(Cx43)在老年大鼠心室肌中的表达及急性心肌缺血时迷走神经刺激对老年大鼠缺血性室性心律失常的影响.方法 结扎大鼠冠状动脉前降支制备急性心肌缺血模型,随机分为(1)成年组:假手术组(SO,n=10)、心肌缺血组(MI,n=15)、心肌缺血+迷走神经刺激组(MI-VNS,n=15)、心肌缺血+迷走神经刺激+阿托品(0.5 mg/kg)组(MI-VNS-Atr,n=13)和心肌缺血+迷走神经刺激+生胃酮(10 mg/kg)组(MI-VNS-CBX,n=11).(2)老年组:假手术组(SO,n=10)、心肌缺血组(MI,n=15)、心肌缺血+迷走神经刺激组(MI-VNS,n=15)、心肌缺血+迷走神经刺激+阿托品(0.5 mg/kg)组(M1-VNS-Atr,n=13)和心肌缺血+迷走神经刺激+生胃酮(10 mg/kg)组(MI-VNS-CBX,n=11).心电图监测室性心律失常的发生.Western blot分析Cx43蛋白表达变化.结果 结扎冠状动脉30 min内,老年MI组室性心动过速(室速)和心室颤动(室颤)发生率较成年MI组显著增加(P＜0.05);老年MI-VS组室速和室颤发生率与老年MI组相比差异无统计学意义(P＞0.05),但老年MI-VS组不可逆性室颤发生率较老年MI组明显减少(P＜0.05).冠状动脉结扎30 min后,缺血没有引起成年组和老年组的总Cx43含量改变(P＜0.05);但缺血引起成年组和老年组的非磷酸化Cx43含量明显增加,迷走神经刺激能够明显抑制成年组和老年组中缺血引起的Cx43脱磷酸化(P＜0.05);而阿托品和生胃酮明显阻断了迷走神经刺激抑制缺血引起的Cx43脱磷酸化的作用(P＜0.05).但实验发现老年SO组Cx43表达较成年SO组明显减少(P＜0.05).结论 老年大鼠缺血性室性心律失常发生率明显增加,而迷走神经刺激的抗缺血性室性心律失常的效应明显减弱,其机制可能与老年大鼠心室肌Cx43表达较成年大鼠明显减少有关.     

环孢霉素A干预钙调神经磷酸酶信号通路对持续心房起搏犬心房Cx40/Cx43表达的影响

目的: 观察钙调神经磷酸酶抑制剂环孢霉素A（CsA）对持续心房起搏（atrial tachypacing,ATP）模型犬心房中Cx40/Cx43表达分布的影响,探讨CsA抑制钙调神经磷酸酶信号通路（CaN）激活是否具有一定的抗心房重构的作用。方法: 健康杂种犬18只,随机分为对照组（sham组）、心房快速起搏组（ATP组,植入固律型单腔起搏器,以400次/min持续起搏8周）及CsA干预组(在快速心房起搏组处理因素的基础上,喂食CsA 8周),每组6只。8周后,处死所有实验犬,采用免疫荧光染色法及蛋白印迹法,检测各组实验犬心房组织中Cx40/Cx43表达及分布的情况。结果: 持续快速心房起搏8周,可导致犬左右心房中Cx40的表达明显增加（P<0.01）,但CsA干预组Cx40表达增加的程度明显小于ATP组（P<0.05）。Cx40的分布方式,ATP组和CsA干预组均呈现出明显的异质性,均有端端连接减少,侧侧连接增加的现象。Cx43蛋白表达的趋势与Cx40不同:快速起搏8周后,犬左右心房组织中Cx43的表达均明显减少（P<0.01）,但减少的程度CsA干预组小于ATP组（P<0.05）。Cx43的分布方式,ATP组及CsA干预组均表现为异质性增加,端端连接减少,侧侧连接增加。结论: CsA可减少ATP导致的Cx40/43表达的重构性变化,提示CsA可能具有一定的抑制心房重构的作用。     

The influence of carvedilol on atrial connexin 40 after myocardial infarction

OBJECTIVE: The purpose of the present study was to study the influence of left ventricular myocardial infarction on gap junction protein connexin 40 in the atria, and to observe the intervention function of carvedilol as an adrenergic receptor blocker. METHODS AND RESULTS: Thirty New Zealand rabbits were randomly divided into three experimental groups: myocardial infarction, carvedilol and control groups. The left anterior descending coronary artery was ligated in animals in the myocardial infarction group; in the control animals no artery was ligated. The animals in the carvedilol group were administered carvedilol by way of gavages at a dose of 0.5 mg/kg. After the experiment had gone on for 8 weeks, the spatial distribution and the amount of gap junction protein connexin 40 in the left auricle ware measured by fluorescence immunohistochemistry and Western blot, respectively. Compared with the controls, the amount of left atrial appendage gap junction protein connexin 40 in the myocardial infarction group was significantly decreased (P < 0.01), and an uneven distribution of gap junction protein connexin 40 was markedly observed. The amount of gap junction protein connexin 40 in the carvedilol group was higher than that in the myocardial infarction group (P < 0.05), and the uneven distribution was minimized in animals with carvedilol administration. CONCLUSION: Left ventricular myocardial infarction can cause a remodelling of gap junction protein connexin 40 in the atria, which becomes distributed with a high heterogeneity and is significantly decreased in the amount of protein. Carvedilol can reduce this remodelling of gap junction protein connexin 40.