OBJECTIVETo investigate the general pattern of cholinergic nerve distribution and M(2) receptors in adult rat heart.

METHODSKarnovsky-Roots histochemical staining combining point counting method and immunochemical SABC method with image analysis were used to identify the cholinergic nerves and M(2) receptors, respectively, in adult rat heart.

RESULTSPositive staining of cholinergic nerves and M(2) receptors was found in all regions of the rat heart, and the point count of cholinergic nerves in the atria was 4.6 times as much as that in ventricles, and the area of immunoreactive substance for M(2) receptors two-fold higher in the atria than in the ventricles. The point counts of the cholinergic nerves in the medial-layer myocardium were fewer than that in subepicardial and endocardial tissues of the left ventricular free wall. However, M(2) receptors were comparable among the 3 layers of the left free ventricular wall.

CONCLUSIONCholinergic nerves and M(2) receptors are located in both rat atria and ventricles, but their density is much higher in the atria than in the ventricles. Transmural heterogeneity characterizes cholinergic nerve innervation in the left ventricular free wall without significant differences in M(2) receptor density.

Animals ; Cholinergic Fibers ; metabolism ; Female ; Heart ; innervation ; Heart Atria ; innervation ; metabolism ; Heart Ventricles ; innervation ; metabolism ; Immunohistochemistry ; Male ; Myocardium ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptor, Muscarinic M2 ; analysis

BACKGROUND: It was known that conventional stress-redistribution imaging was not adequate for detection of severely ischemic but viable myocardium. Albeit the gold criteria of viable myocardium is the presence of metabolism which can be detected by PET, reinjection technique was reported to be able to identify most, if not all, of viable myocardium. Because reinjection imaging is performed immediately after redistribution imaging, an additional redistribution could be happened if we follow the patient longer. To prove the guess authors performed an additional delayed imaging 24 hours after reinjection of 201T1. METHODS: Subject patients were 20 ischemic heart disease patients who showed irreversible perfusion defect(s) on standard pharmacologic(dipyridamole) stress-redistribution images. Immediately after the redistribution images were obtained, 37 MBq thallium was injected at rest, and images were reacquired at 10 minutes and 24 hours after reinjection. Four sets of images(stress, redistribution, reinjection and delayed images) were then analyzed qualitatively and quantitatively. Left ventricle was arbitrarily divided into 9 segments(apex, proximal and distal portions of anterior, septal, inferior and lateral walls). RESULTS: These were 45 irreversible perfusion defects in 20 subject patients, of which 21(46.7%) showed improved thallium uptake after reinjection. Among these 21 segments 2 demonstrated further improvement of uptake on 24-hour delayed images, of the 24 regions determined to have persistent defects after reinjection. 10(41.7%) showed improved uptake on delayed images. CONCLUSIONS: In addition to reinjection imaging, 24-hour delayed imaging after reinjection was also helpful to identify severely ischemic but viable myocardium.
Dipyridamole* ; Heart Ventricles ; Humans ; Metabolism ; Myocardial Ischemia ; Myocardium* ; Perfusion ; Thallium ; Tomography, Emission-Computed, Single-Photon*

The chronic effects of carboxyl-terminal polypeptide of Cardiotrophin-1 (CT-1-CP) on ventricular electrical remodeling were investigated. CT-1-CP, which contains 16 amino acids in sequence of the C-terminal of Cardiotrophin-1, was selected and synthesized, and then administered to Kunming mice (aged 5 weeks) by intraperitoneal injection (500 ng·g⁻¹·day⁻¹) (4 groups, n=10 and female: male=1:1 in each group) for 1, 2, 3 and 4 weeks, respectively. The control group (n=10, female: male=1:1) was injected by physiological saline for 4 weeks. The epicardial monophasic action potential (MAP) was recorded by using a contact-type MAP electrode placed vertically on the left ventricular (LV) epicardium surface, and the electrocardiogram (ECG) signal in lead II was monitored synchronously. ECG intervals (RR, PR, QRS and QT) and the amplitude of MAP (Am), the maximum upstroke velocity (Vmax), as well as action potential durations (APDs) at different repolarization levels (APD30, APD50, APD70, and APD90) of MAP were determined and analyzed in detail. There were no significant differences in RR and P intervals between CT-1-CP-treated groups and control group, but the PR segment and the QRS complex were greater in the former than in the latter (F=2.681 and 5.462 respectively, P<0.05). Though QT interval and the corrected QT interval (QTc) were shorter in CT-1-CP-treated groups than in control group, the QT dispersion (QTd) of them was greater in the latter than in the former (F=3.090, P<0.05) and increased with the time. The ECG monitoring synchronously with the MAP showed that the compression of MAP electrode on the left ventricular epicardium induced performance similar to myocardium ischemia. As compared with those before chest-opening, the PR segment and QT intervals remained basically unchanged in control group, but prolonged significantly in all CT-1-CP-treated groups and the prolongation of QT intervals increased gradually along with the time of exposure to CT-1-CP. The QRS complex had no significant change in control group, one-week and three-week CT-1-CP-treated groups, but prolonged significantly in two-week and four-week CT-1-CP-treated groups. Interestingly, the QTd after chest-opening was significantly greater than that before chest-opening in control group (t=5.242, P<0.01), but decreased along with the time in CT-1-CP-treated groups. The mean MAP amplitude, Vmax and APD were greater in CT-1-CP-treated groups than those in control group, and became more obvious along with the time. The APD in four CT-1-CP-treat groups was prolonged mainly in middle to final repolarization phase. The difference among these groups became significant in middle phase (APD50) (F=6.076, P<0.01) and increased furthermore in late and final phases (APD70: F=10.054; APD90: F=18.691, P<0.01) along with the time of injection of CT-1-CP. The chronic action of CT-1-CP might induce the adapting alteration in cardiac conductivity and ventricular repolarization. The amplitude and the Vmax of the anterior LV epicardial MAP increased obviously, and the APD prolonged mainly in late and final phase of repolarization.
Animals ; Cytokines ; chemistry ; physiology ; Electrocardiography ; Heart Ventricles ; metabolism ; Mice ; Peptide Fragments ; physiology ; Ventricular Function

OBJECTIVETo explore potential divergent glycolytic metabolism gene changes between left and right ventricle in the monocmtaline (MCT) induced pulmonary arterial hypertension (PAH) rat model.

METHODSPAH was induced by a single subcutaneous injection of MCT (50 mg/kg) in rats. Control rats were injected with normal saline. MCT-PAH rats were randomly divided into MCT-2week, MCT-3week and MCT-4week groups (MCT-2w, 3w, 4w). At the end of study, the hemodynamics and right ventricular hypertrophy were compared among groups. The expression levels of proliferating cell nuclear antigen (PCNA) and TdT-mediated dUTP nick end labeling (TUNEL) in left and right ventricular cells were compared. The glycolytic key candidate genes expression was screened between two ventricles.

RESULTSAfter three to four weeks MCT injection, mean pulmonary arterial pressure, right ventricular systolic pressure and right ventricular hypertrophy index were all significantly increased compared to control group (all P < 0.05). Both left and right ventricular morphology and structure changes were observed in all PAH rats and were similar between left and right ventricular cells. Left and right ventricular cells increased while apoptotic cells decreased in proportion to the duration post MCT injection and the PCNA positive cells in the right ventricle were higher than in the left ventricle in rats post 3 and 4 weeks MCT injection (P < 0.05). The HK1, HK2, PDHα1 and LDHA mRNA expression in the left ventricle and LDHA mRNA expression were significantly upregulated after 4 weeks MCT injection compared to control rats (all P < 0.05). Moreover, HK1 mRNA expression in the left ventricle was significantly higher in the MCT-PAH-4w group than in MCT-PAH-3w group (P < 0.05). Immunohistochemistry analysis evidenced increasing HK1 positive cells in both left and right ventricle in proportion to MCT injection time and positive HK1 cells were significantly higher in the right ventricle than in left ventricle of MCT-PAH-3w and MCT-PAH-4w rats. Furthermore, the HK1 protein expression in left ventricular tissue form MCT-PAH-4w group and in right ventricular tissue from MCT-PAH-3w and MCT-PAH-4w groups were also significantly upregulated compared to control group (P < 0.05).

CONCLUSIONSEnergy metabolic shift occurs both in the left and right ventricles in this PAH model. Upregulated HK1 expression appeares earlier in right ventricle compared to left ventricle. Interference on right ventricular glycolysis may be a potential novel therapy target of PAH.

Animals ; Gene Expression ; Heart Ventricles ; metabolism ; Hemodynamics ; Hypertension ; Hypertension, Pulmonary ; metabolism ; Hypertrophy, Right Ventricular ; metabolism ; Lung ; Monocrotaline ; Rats

BACKGROUND AND OBJECTIVES: Left ventricle burdened by longstanding volume-overload, undergoes various structural and functional alterations. Accordingly, the expressions of multiple classes of genes are likely to be altered. However, the profile of gene expressions, specifically in a volume-overloaded left ventricle in humans, has not been explored. SUBJECTS AND METHODS: The pattern of gene expression was studied, using a cDNA microarray, in myocardium from 4 normal subjects and 5 patients with chronic regurgitant valvular heart disease whose end-diastolic left ventricular dimension measures 65 mm or more, but whose systolic function remained preserved. RESULTS: We identified 58 differentially expressed genes that were functionally classifiable in the volume-overloaded myocardium. Those genes involved in cell cycle/growth (up/down-regulation: 9/1), signal transduction (4/1) were mostly overexpressed in the volume-overloaded myocardium. The distributions of the gene expressions were variable for those involved in transcription/translation (up/down-regulation: 6/7) and apoptosis (2/2). The genes related to the myocyte structure (troponin T3, tropomyosin, etc)(up/down-regulation: 1/10), as well as those related to metabolism (2/5), were underexpressed. The gene expression patterns from RT-PCR and Western blot, with randomly selected genes, were similar to those from the cDNA microarray. CONCLUSION: Altered expression was identified in multiple genes in the volume-overloaded human left ventricle prior to the development of heart failure. The genes related to cell growth and signal transduction were mostly overexpressed, while those related to cellular structure and metabolism appeared to be underexpressed. These results might help in the elucidation of cellular mechanisms for the remodeling process associated with chronic volume-overloading.
Apoptosis ; Blotting, Western ; Cellular Structures ; Gene Expression* ; Heart Failure* ; Heart Valve Diseases ; Heart Ventricles ; Heart* ; Humans* ; Metabolism ; Muscle Cells ; Myocardium* ; Oligonucleotide Array Sequence Analysis ; Signal Transduction ; Transcriptome* ; Tropomyosin

One of the major circulatory changes that occur in human during space flight and simulated weightlessness is a cerebral redistribution of body fluids, which is accompanied by an increase of blood volume in the upper body. Therefore, atrial myocardium should increase the secretion of atrial natriuretic peptide (ANP), but the researches lack common conclusion until now. The present study was to investigate the expression level of ANP in simulated weightlessness rats, and to confirm the changes of ANP by observing the associated proteins of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The tail-suspended rat model was used to simulate weightlessness. Western blots were carried out to examine the expression levels of ANP and SNARE proteins in atrial and left ventricular myocardium. The results showed that ANP expression in atrial myocardium showed an increase in 4-week tail-suspended rats (SUS) compared with that in the synchronous control rats (CON). We only detected a trace amount of ANP in the left ventricular myocardium of the CON, but found an enhanced expression of ANP in left ventricular myocardium of the SUS. Expression of VAMP-1/2 (vesicle associated SNARE) increased significantly in both atrial and left ventricular myocardium in the SUS compared with that in the CON. There was no difference of the expression of syntaxin-4 (target compartment associated SNARE) between the CON and SUS, but the expression of SNAP-23 showed an increase in atrial myocardium of the SUS compared with that in the CON. Synip and Munc-18c as regulators of SNAREs did not show significant difference between the CON and SUS. These results suggest that the expression of ANP shows an increase in atrial and left ventricular myocardium of 4-week tail-suspended rats. Enhanced expression of VAMP-1/2 associated with ANP vesicles confirms the increased expression of ANP in atrial and left ventricular myocardium.
Animals ; Atrial Natriuretic Factor ; metabolism ; Heart Ventricles ; metabolism ; Myocardium ; metabolism ; Rats ; SNARE Proteins ; metabolism ; Vesicle-Associated Membrane Protein 1 ; metabolism ; Vesicle-Associated Membrane Protein 2 ; metabolism ; Weightlessness Simulation

Autonomic nervous system plays an important role in the regulation of mammalian heart, and it is divided into the sympathetic and parasympathetic (vagal) subsystems. The parasympathetic (vagal) control of the atria involves modulation of chronotropic, dromotropic and inotropic activities, but the role of the parasympathetic innervation of the ventricles is still unclear. There is a common misconception that the sympathetic nerves innervate all over the heart; while the parasympathetic nerves only innervate the superventricular part of the heart, but not the ventricles. Recent evidence indicates that the cholinergic innervation of the left ventricle is functionally very important in some mammalian species. The present article reviews the evidence of vagal control in the ventricles from the anatomy and histochemistry, molecular biology, and function areas. Additionally we overview the vagal (muscarinic) regulation of cardiac contractile function and its signal transduction.
Animals ; Heart Ventricles ; anatomy & histology ; innervation ; metabolism ; Humans ; Myocardial Contraction ; physiology ; Receptors, Muscarinic ; metabolism ; Signal Transduction ; physiology ; Vagus Nerve ; physiology

To explore the role of mechanosensitive potassium channel TREK-1, Western blot analysis was used to investigate the expression changes of TREK-1 in left ventricle in acute mechanically stretched heart. Forty Wistar rats were randomly divided into 8 groups (n=5 in each group), subject to single Langendorff perfusion for 0, 30, 60, 120 min and acute mechanical stretch for 0, 30, 60, 120 min respectively. With Langendorff apparatus, an acute mechanically stretched heart model was established. There was no significant difference in the expression of TREK-1 among single Langendorff perfusion groups (P>0.05). As compared to non-stretched Langendorff-perfused heart, only the expression of TREK-1 in acute mechanically stretched heart (120 min) was greatly increased (P<0.05). This result suggested that some course of mechanical stretch could up-regulate the expression of TREK-1 in left ventricle. TREK-1 might play an important role in mechanoelectric feedback, so it could reduce the occurrence of arrhythmia that was induced by extra mechanical stretch.
Feedback ; Heart Ventricles/*metabolism ; Mechanotransduction, Cellular ; Potassium Channels, Tandem Pore Domain/*metabolism ; Random Allocation ; Rats, Wistar ; Stress, Mechanical

AIMTo observe the effects of adenosine on intracellular calcium concentration ([Ca2+]i) level in guinea pig ventricular myocytes and to define the possible mechanisms involved.

METHODSThe effects of adenosine on [Ca2+]i were investigated in guinea pig ventricular myocytes. [Ca2+]i was detected by laser confocal microscopy and represented by relative fluorescent intensity ((FI-FI0)/FI0, %, FIo: control, FI: administration of drugs).

RESULTS(1) Adenosine (10, 50, 100 micromol/L) reduced [Ca2+]i of ventricular myocytes in both normal Tyrode's solution and Ca(2+) -free Tyrode's solution in a concentration-dependent manner. (2) Tyrode's solution containing 30 mmol/L KCl (high K+ Tyrode's solution) induced [Ca2+]i elevation in ventricular myocytes, while adenosine (10, 50, 100 micromol/L) markedly inhibited the increase in [Ca2+]i induced by KCl. (3) Pretreatment with DPCPX (1 micromol/L) significantly reduced the effects of adenosine (100 micromol/L) in high K+ Tyrode's solution. The effects of adenosine (100 micromol/L) on [Ca2+]i in high K+ Tyrode's solution were also partially attenuated by pretreatment with L-NAME (1 mmol/L). (4) Adenosine (100 micromol/L) markedly inhibited the low concentration of ryanodine-induced [Ca2+]i increase in Ca(2+) -free Tyrode's solution. (5) When the propagating waves of elevated [Ca2+]i (Ca2+ waves) were produced by increasing extracellular Ca2+ concentration from 1 mmol/L to 10 mmol/L, adenosine (100 micromol/L) could block the propagating waves of elevated [Ca2+]i, reduce the frequency and duration of propagating waves, and reduce [Ca2+]i as well.

CONCLUSIONAdenosine may reduce the [Ca2+]i in isolated guinea pig ventricular myocytes via inhibiting Ca2+ influx and alleviating Ca2+ release from sarcoplasmic reticulum(SR). The reduction of Ca2+ influx might be due to the inhibition of voltage-dependent Ca2+ channel via adenosine A1 receptor, and NO might be involved in this process.

Adenosine ; pharmacology ; Animals ; Calcium ; metabolism ; Cells, Cultured ; Guinea Pigs ; Heart Ventricles ; cytology ; Myocytes, Cardiac ; drug effects ; metabolism

The purpose of this study was to investigate the different effects of ACh on the action potential and force contraction in guinea pig atrial and ventricular myocardium by using standard microelectrodes and force transducer. The results showed that the duration of the action potential (APD) of atrial myocardium was shortened from 208.57+/-36.05 to 101.78+/-14.41 ms (n=6, P<0.01), and the APD of the ventricular myocardium was shortened from 286.73+/-36.11 to 265.16+/-30.06 ms (n=6, P<0.01).The amplitude of the action potential (APA) of the atrial myocardium was decreased from 88.00+/-9.35 to 62.62+/-20.50 mV (n=6, P<0.01), while the APA of the ventricular myocardium did not change significantly.The force contraction of atrial myocardium was inhibited completely (n=6, P<0.01), while the force contraction of ventricular myocardium was inhibited by 37.57+/-2.58% (n=6, P<0.01). The ACh effects correlated with its concentration. The K(D) of the APD shortening effects in the atrial and ventricular myocardium were 0.275 and 0.575 micromol/L. The K(D) of the negative inotropic in the atrial and ventricular myocardium were 0.135 and 0.676 micromol/L, respectively. The corresponding data points were compared using t test between the atrial and ventricular myocardium, and the differences were significant when the ACh concentration was above 10 nmol/L. Furthermore, atropine (10 micromol/L) and CsCl (20 mmol/L) blocked the effects of 10 micromol/L ACh on the APD of ventricular myocardium, while CdCl2 (0.1 mmol/L) had no influence on these effects. In conclusion, ACh could shorten the action potential duration and inhibit the force contraction of atrial and ventricular myocardium in a concentration-dependent manner. There are differences in the effects of ACh on the atrial and ventricular myocardium. The atrial myocardium is more sensitive to ACh than the ventricular myocardium. It is probable that the muscarinic receptor and the potassium channel, but not the calcium channel, are involved in the ACh-induced shortening of the ventricular APD.
Acetylcholine ; pharmacology ; Action Potentials ; drug effects ; Animals ; Calcium Channels ; metabolism ; Guinea Pigs ; Heart Atria ; drug effects ; Heart Ventricles ; drug effects ; Microelectrodes ; Potassium Channels ; metabolism ; Receptors, Muscarinic ; metabolism