Effects of pioglitazone on myocardial energy metabolism and hemodynamics in rats with myocardial infarction

AIM: To observe the effects of pioglitazone on myocardial energy metabolism and hemodynamics in rats with heart failure after myocardial infarction (MI). METHODS: The model of MI was established by ligation of left anterior descending artery. The 20 surviving rats were randomly divided into MI group (n=10) and pioglitazone intervention group (P group,n=10, pioglitazone 3 mg·kg^-1·d^-1 orally). The sham-operated rats (SH, n=10) served as controls. Hemodynamic parameters were measured. The ratio of left ventricular weight to body weight (LVW/BW) and the ratio of right ventricular weight to body weight (RVW/BW) were calculated after 8-week treatment. The expression of PPARγ was examined by Western blotting. Mitochondrial respiratory function was determined by Clark oxygen electrodes. The size of adenine acid pool (ATP, ADP and AMP) in mitochondria was measured by HPLC. The adenine nucleotide translocator(ANT) activity was detected by the atractyloside-inhibitor stop technique. RESULTS: Compared with SH group, the protein expression of PPARγ was significantly decreased in MI group (P<0.01). The mitochondrial respiratory activity, the transport activity of ANT and the high-energy phosphate content were decreased in MI group (P<0.01), and the hemodynamic parameters were in disorder (P<0.01). Compared with MI group, the protein expression of PPARγ in P group was significantly increased. The mitochondrial respiratory activity, the high-energy phosphate content, the transport activity of ANT were improved (P<0.01). However, the hemodynamic parameters were not significantly changed.CONCLUSION: Pioglitazone increases the protein expression of PPARγ and improves myocardial energy metabolism in the development of heart failure in the rat model of myocardial infarction, but dose not change the hemodynamic parameters significantly.     

Correlation between myocardial interstitial collagen remodeling and changes in hemodynamics in rats with myocardial infarction

AIM: To study the relationship between cardiac extracellular matrix remodeling and cardiac function after myocardial infarction. METHODS: We observed sequential changes in collagen contents and collagen Ⅰ/Ⅲ ratios in infarct zone (IZ) and non-infarct zone (NIZ) and their relationship to the parameters of left ventricular systolic and diastolic function in the rat model of myocardial infarction induced by ligation of left main coronary artery. RESULTS: Collagen conteants in IZ and NIZ after 3d of myocardial infarction were significantly higher than those in sham group at corresponding time (P<0.05, P<0.01). Collagen Ⅰ/Ⅲ ratio in IZ decreased on day 3, significantly increased after 7 d (P<0.01). Collagen Ⅰ/Ⅲ ratio in NIZ increased significantly afte14 d. Correlated analysis between collagen contents in IZ or NIZ and collagen type Ⅰ/Ⅲ ratio and maximal ascending velocity (+p'_max) or maximal descending velocity of the left ventricular pressure (-p'_max) was performed and the negative correlation between collagen contents in NIZ and +P'_max (r=-0.589, P>0.05) and -P'_max (r=-0.788, P<0.01) was found. Collagen content in IZ positively correlated to the +P'_max (r=0.70, P<0.50), but not to -P'_max (r=-0.29, P>0.05). Collagen type Ⅰ/Ⅲ ratios in NIZ correlated negatively to the +P'_max (r=-0.504, P>0.05) and -P'_max (r=-0.545, P>0.05), but there were no relationship between collagen type Ⅰ/Ⅲ ratios in IZ and +P'_max or -P'_max in IZ. CONCLUSION: Collagen deposition in IZ after myocardial infarction was of benefit to improvement of systolic function. Collagen deposition in NIZ was harmful to systolic and diastolic function.     

MicroRNA profile analysis of ischemic myocardial tissues from rats with acute myocardial infarction

AIM：To identify differentially expressed microRNAs (miRNAs) in ischemic myocardial tissues from the rats with acute myocardial infarction (AMI) by miRNA array technique, and to predict their targets and analyze their functions using bioinformatics. METHODS：The rat models of AMI (n=3) were prepared by ligaturing the left anterior descending coronary artery (LAD) of Wistar rats. Electrocardiogram and blood pressure were detected during the operation, and the myocardial infarct size was measured by 2, 3, 5-triphenyltetrazolium chloride (TTC) staining. Ischemic myocardial tissues were isolated from the infarct area 4 h after ischemia. The same procedure in sham group (n=3) was performed except for ligaturing LAD. Total RNA was extracted from ischemic and normal myocardial tissues. miRNA was isolated from total RNA, labeled with Cy3 and hybridized on miRNA array. Real-time PCR was applied to verify the reliability of miRNA array results. The targets of differentially expressed miRNAs were predicted and their functions were analyzed by bioinformatics. RESULTS：Rat model of AMI was successfully prepared and verified by electrocardiogram detection, blood pressure measurement and pathological observation. Compared with sham group, microarray screening showed that total 11 AMI-related miRNAs were selected, including 6 up-regulated and 5 down-regulated. Three of them (rno-miR-181c, rno-miR-146b and rno-miR-208) were related to the cardiovascular functions, while the functions of the others (rno-miR-672*, rno-miR-743b, rno-miR-128, rno-miR-138-1*, rno-miR-336, rno-miR-138-2*, rno-miR-325-3p and rno-miR-3572) were unknown and might be novel AMI-related biomarkers. Parts of the miRNA targets were also related to the cardiovascular functions. CONCLUSION：Differentially expressed miRNAs in AMI rats may serve as novel biomarkers for diagnosis of AMI and potential targets for treatment of AMI.     

Cardiomyocyte apoptosis and expression of Bcl-2, Bax protein after acute myocardial infarction and late reperfusion in dogs

AIM: To study the effect of late reperfusion on apoptotic cardiomyocytes in the risk area of acute myocardial infarctin in dogs. METHODS: The experiment was divided into three groups: sham operation group, acute myocardial infarction (AMI) group, and late reperfusion (LR) group. Apart from sham operation group, the other two groups were subjected to left anterior descending branch of coronary artery ligation. The acute myocardial infarction group was only subjected to ligation for 12 hours, late reperfusion group was subjected to ligation for 6 hours following by 6 hours of reperfusion. The cardiomyocyte apoptosis was measured by TUNEL assay. Immunohistochemistry and Western blotting analysis were used to detect the expression of Bcl-2 and Bax protein. RESULTS: The number of apoptotic cardiomyocytes in late reperfusion group was much less than acute myocardial infarction group (P<0.05), and increased significantily as compared with sham operation group (P<0.01). The expression of Bcl-2 protein was enhanced gently in late reperfusion group in contrast to acute myocardial infarction group, but no significant difference in the two groups (P>0.05) was observed, although it was much more in the two groups than that in sham operation group (P<0.01). The expression of Bax protein in late reperfusion group was much higher than that in sham operation group (P<0.01), and was lower than that in acute myocardial infarction group (P<0.05). CONCLUSION: Late reperfusion reduces cardiomyocyte apoptosis in the risk area of acute myocardial infarction. The mechanism may be that late reperfusion can decrease the expression of Bax protein.     

Salvia extract promotes angiogenesis of myocardium in rats with myocardial infarction

AIM: To determine the effect of salvia extract on angiogenesis of the myocardium in the rats with myocardial infarction (MI) and to analyze its possible mechanism. METHODS: Left coronary artery of Sprague-Dawley rats was ligated to establish a MI model. The rats were randomly divided into MI model group, 3 different dose groups of salvia (10, 20 and 40 mg·kg^-1·d^-1), and sham operation group. Each group consisted of 8 rats. The rats in all treatment groups were orally administered with the salvia extract, and the rats in MI group and sham operation group were fed with the same volume of saline. The rats were sacrificed 4 weeks later. The hemodynamic changes of the rats were determined, and the segmental heart samples were used for morphological observation by hematoxylin and eosin staining, Masson staining, or electron microscopic analysis. The expression of vascular endothelial growth factor (VEGF) and cluster of differentiation 34 (CD34) was analyzed according to immunohistochemistry. RESULTS: Compared with sham operation group, the morphological changes of the myocardium in MI group were disordered, part of myocardial cell outline disappeared, and obvious fibrosis in the necrosis myocardial tissue and fuzzy or disappearing microvascular ultrastructure were also observed. Compared with MI group, the number of new microvessels in all the treatment groups increased obviously, and the morphological changes of the endothelial cells were relatively complete according to electron microscopy. Compared with sham operation group, the protein expression of VEGF and CD34 in the cytoplasm of the myocardial tissues in MI group increased only a little. Compared with MI group, the protein expression of VEGF and CD34 in the cytoplasm of the myocardial tissues in all treatment groups increased significantly (P<0.01). CONCLUSION: Salvia extract obviously promotes angiogenesis of the myocardial tissues in the rats after myocardial infarction.     

Changes of potassium currents in rabbit ventricle with healed myocardial infarction

AIM: To elucidate the mechanism of arrhythmia in healed myocardial infarction (HMI), and to investigate the changes of action potential duration (APD),transient outward potassium current (I_to), delayed rectifier potassium current (I_K) and inward rectifier potassium current (I_K1) of left ventricular myocytes in noninfarcted zone of HMI. METHODS: 12 rabbits were randomly assigned in two groups: HMI group (thoracotomy and ligation of the circumflex coronary); sham-operated group (thoracotomy but no conorary ligation). 3 months after operation, whole cell patch clamp technique was used to record APD, I_to, I_K and I_K1 of ventricular myocytes in non-infarcted zone. RESULTS: Membrane capacitance was larger in HMI group than that in sham-operated group. Action potential duration was lengthened significantly in HMI group and early after depolarization (EAD) appeared in HMI group. The densities of I_to, I_K,tail and I_K1 were reduced significantly in HMI group (P<0.01), from (6.72±0.42) pA/pF, (1.54±0.13) pA/pF and (25.6±2.6) pA/pF in Sham-operated group to (4.03±0.33) pA/pF, (1.14±0.11) pA/pF and (17.6±2.3) pA/pF, respectively. CONCLUSION: The reduced densities of I_to, I_K,tail and I_K1 in ventricular myocytes of non-infarcted zone in HMI are responsible for the prolongation of APD and the presentation of EAD, which play important roles in the malignant arrhythmia of HMI.     

Effect of angelica on myocardial fibrosis post myocardial infarction in rats

AIM: To investigate 1) the role of transforming growth factor-β₁ (TGF-β₁) and macrophage infiltration during the development of myocardial fibrosis (MF) in rats after myocardial infarction (MI);and 2) mechanisms of MF post-MI and the inhibitory effect of angelica.METHODS: Sprague-Dawley (SD) rats were subjected to MI by ligating the left anterior descending coronary artery.The animals were randomly divided into three groups: sham, MI and MI+angelica.After 24 hours of ligation, rats received angelica (20 mL·kg^-1·d^-1, ip) or saline.Left ventricular hemodynamics were measured and rats were killed at week 1, week 2 and week 4, respectively.Collagen content, macrophage infiltration and TGF-β₁ expression were examined in the non-infarcted area.RESULTS: ① In MI group, the numbers of macrophage and TGF-β₁ expression were significantly upregulated compared to sham at week 1 post-MI and remained elevated at week 4 (P<0.01).Angelica significantly decreased macrophage infiltration and TGF-β₁ expression (P<0.01 vs MI).② Collagen content was increased significantly in MI group compared to sham at week 2 and week 4 (P<0.01), and decreased in MI+angelica group (P<0.05 vs MI).③ Cardiac function was markedly decreased post-MI in MI group (P<0.01), and improved at week 4 in MI+angelica group (P<0.05).CONCLUSION: In MF post-MI, angelica may have an antifibrotic effect by decreasing macrophage infiltration and TGF-β₁ expression, by which reactive myocardial fibrosis is reduced, and cardiac function is improved.     

Changes of cytokine and collagen in the myocardial remodeling after acute myocardial infarction in rats

AIM:To clarify the relationship between the cytokine and collagen in myocardial remodeling after acute myocardial infarction (MI) in rats. METHODS:In MI group, Wistar rats were undergone acute myocardial infarction by ligation of the anterior descending coronary artery. Sham operation was made in rats as control. The mRNA expression of collagen and cytokines such as TNF-α and TGF-β1 in infract and non-infarct region of left myocardium were detected by RT-PCR at different time point (3 d, 1 and 4 weeks). RESULTS:Collagen type Ⅰ and Ⅲ elevated as well as the TNF-α and TGF-β1 in the MI group at 3th day. Expression of collagen type Ⅰ and Ⅲ were higher in the infarct region than that in the non-infarct region even at 4 weeks. TNF-α and TGF-β1 peaked at 1 week and declined gradually to the baseline, which was still higher than those in control group (P<0.01). Correlation analysis revealed that expressions of TNF-α and TGF-β1 were positively correlated with the collagen type Ⅰand Ⅲ (P<0.01). CONCLUSION:Cytokines participate in the myocardial remodeling after MI. Interfering with expression of cytokines may be the potentially preventative method in the myocardial remodeling.     

Effects of atorvastatin on release of endothelial microparticles and myocardial apoptosis in rats with acute myocardial infarction

AIM: To investigate the effect of atorvastatin(AT) on the release of endothelial microparticles(EMP) and myocardial apoptosis in the rats with myocardial infarction. METHODS: SD male rats(n=24) were randomly divided into 3 groups:sham operation(sham) group, myocardial infarction(MI) group and MI+AT group. The rat model of acute myocardial infarction was prepared by coronary artery ligation. At 2 h and 24 h after modeling, the peripheral blood was collected to detect creatine kinase-MB(CK-MB) and cardiac troponin T(cTnT). The circulating levels of EMP were measured by flow cytometry. The myocardial apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling(TUNEL) assay. RESULTS: At 2 h after modeling, the level of CK-MB was significantly increased in MI group compared with sham group, and the level of EMP and the myocardial apoptotic rate were significantly increased in MI group and MI+AT group compared with sham group. At 24 h after modeling, the level of EMP was significantly increased in MI group compared with sham group. The levels of CK-MB, cTnT, EMP and the myocardial apoptotic rate were significantly decreased in MI+AT group compared with MI group. Moreover, the level of CK-MB in MI group was significantly increased at 24 h compared with that at 2 h after modeling. The levels of CK-MB, cTnT and EMP were significantly decreased in MI+AT group at 24 h compared with those at 2 h after modeling. CONCLUSION: Ator-vastatin may reduce the level of EMP and the myocardial apoptotic rate in the rats with acute myocardial infarction, indicating that atorvastatin plays a role in protecting endothelium.     

Effect of Shenshuguanxin granula on coronary circulation in rats with myocardial infarction

AIM：To explore the effect of traditional Chinese medicine Shenshuguanxin granula on coronary circulation in a rat model of myocardial infarction (MI). METHODS：SD rats (n=50, SPF grade) were randomly divided into 5 groups (n=10):sham group, MI group, and high-dose, middle-dose and low-dose Shenshuguanxin granula treatment groups. The rat MI model was established by ligation of the coronary artery. The cardiac markers, small and medium-sized blood vessels ［microvessel count (MVC) value］ in the infarct zone, and platelet endothelial cell adhesion mo-lecule 1 (PECAM-1) and vascular endothelial growth factor (VEGF) expression in the infarct border zone were measured. RESULTS：After 4 weeks of coronary artery ligation, the significant increases in MVC in the infarct zone, and the expression of PECAM-1 and VEGF in the infarct border zone were detected compared with sham group (P<0.05). The differences of cardiac markers between MI group and other groups were insignificant (P>0.05). CONCLUSION:Shenshuguanxin granula improves coronary circulation in the rats with myocardial infarction by increasing the expression of PECAM-1 and VEGF, and promoting small and medium-sized angiogenesis.     

Early-phase changes of parameters related to myocardial fibrosis in acute myocardial infarction

AIM:To investigate the changes in parameters related to myocardial fibrosis of H2 relaxin (H2RLX) and procollagen type I C-terminal peptide (PICP), transforming growth factor-β1 (TGF-β1) level in the plasma after acute anterior myocardial infarction.METHODS:Forty-one patients with anterior myocardial infarction (MI) and 10 controls with normal coronary vessels were selected.Plasma H2RLX, PICP, and TGF-β1 levels were determined by enzyme linked immunosorbent assay (ELISA) in 10 control subjects and 41 post-MI patients at day 3 and 7 post-MI.RESULTS:(1) H2RLX level at day 3 post-infarct had no difference between the patients and the controls.No marked change in H2RLX at day 3 versus day 7 post-infarct was observed.（2）The level of PICP at day 3 post-infarct was markedly increased followed by a fall at day 7 post-infarct, but was still higher than that in control.(3) TGF-β1 level, which was similar at day 3 and 7 post-infarct, was higher than that in control.(4) At day 7 post-infarct, the level of H2RLX was positively correlated with the fasting blood glucose in MI group.CONCLUSION:In early period of acute MI, profibrotic factors such as TGF-β1 expression and collagen expression increase.However, antifibrotic relaxin has no change.     

Pathophysiological significance of ubiquition-proteasome system in myocardial infarction

Degradation of most proteins in eukaryotic cells is through the ubiquition-proteasome system (UPS). Recently, it demonstrated that UPS regulates cell apoptosis and cardiac hypertrophy. The differences of UPS regulation lie in E3 ligases, which specifically recognize targets and direct the ubiquitination process. Recent evidence suggests that atrogin-1/muscle atrophy F-box (Mafbx) and muscle RING finger 1 (MuRF1) may be critical mediators of the heart and muscle atrophy and hypertrophy. This review summarizes the possible relationship between UPS and cardiac dysfunction after myocardial infarction in order to inhibit cardiac dysfunction after myocardial infarction.     

Effects of external counterpulsation on renin-angiotensin system and hemodynamics in dogs with myocardial ischemia

AIM:To examine the effect of external counterpulsation(ECP) on renin-angiotensin system(RAS) and hemodynamics in dogs with myocardial ischemia and their relationship. METHODS:Acute myocardial ischemia was induced by occluding the left anterior descending of the dogs. The local renin activity, angiotensin Ⅱ(AngⅡ) level, angiotension-converting enzyme(ACE) activity were tested by biochemical methods and hemodynamics was recorded by a 8-channel physiological recorder.RESULTS:Ischemia could actiivate renin,ACE and AngⅡ in cardiovasculature and ECP reduced them except for renin in ischemic myocardium. Ischemia also could activate RAS in lung and kidney, which play an important role on circulating RAS, and ECP reduced them. Furthermore, ECP could improve hemodynamics and there existed a close relationship between local AngⅡlevel and hemodynamics. CONCLUSION:ECP can reduce local RAS and improve hemodynamics in dogs with myocardial ischemia, which might be one of mechanisms underlying the protective effect of ECP on ischemic myocardium.     

Establishment of miniature swine myocardial infarction model by percutaneous balloon occlusion method

AIM: To study the feasibility of establishing miniature swine myocardial infarction(MI)model by percutaneous balloon occlusion method, and to investigate the effect of autologous mesenchymal stem cells(MSCs)transplantation on treatment of acute MI. METHODS: Twenty Tibet miniatrue swine were included in the study and randomly divided into 2 groups. After anaesthesia, 2.5 mm×15.0 mm percutaneous transluminal coronary angioplasty balloon was positioned in the middle and distal-LAD by percutaneous femoral puncture in the right inguinal in the animals. The LAD flow was occluded for 90 min. The electrocardiogram(ECG), echocardiography(UCG), single photon emission computed tomography(SPECT), magnetic resonance imaging(MRI)and histopathology were examined. MSCs suspensions were injected to the infarct myocardium through infarct-related coronary artery by OTW balloon in MSCs transplantation group, while the control swine were injected with normal saline. Left ventricular ejection fraction(LVEF), end diastolic volume(EDV), end systolic volume(ESV)and fractional shortening(FS)were observed. RESULTS: The coronary angiography was successfully performed in all 20 swine. Ten swine survived during the process of balloon occlusion, 10 dead and the success rate reached 50%. After MI, LVEF and FS significantly decreased, while EDV and ESV significantly increased as compared to the values of pre-modeling(P<0.05). Eight weeks after transplantation, the parameters observed above improved in MSCs group as compared to those of pre-transplantation(P<0.05,P<0.01). However, no significant difference of the parameters in saline group between pre-transplantation and after-transplantation was observed. Compared to saline group, LVEF and FS significantly increased in MSCs group(P<0.05,P<0.01)with significant decreases in EDV and ESV(P<0.05,P<0.01). CONCLUSION: The miniature swine MI model is successfully established by percutaneous balloon occlusion method. Stem cells transplantation prevents the occurrence of ventricular fibrillation and obviously improves the myocardial functions.     

Effects of granulocyte colony-stimulating factor on the myocardial infarction in experimental rats

AIM: To investigate the effects of granulocyte colony-stimulating factor (G-CSF) on the myocardial infarction in experimental rats. METHODS: Rats were randomly divided into GT group and saline control group (SC).The rats of GT group were treated with G-CSF (10 μg/kg) once a day subcutaneously for 5 days and those of SC group were received saline.On the third day, both groups were injected with isoprenaline (ISO) interaperitoneally to develop acute ischemic model. The hearts were harvested from 2 weeks to 4 weeks after administration of ISO for histopathological examination. RESULTS: Compared with saline control group, G-CSF treatment group significantly reduced the scar size (P<0.05). We also found the regeneration of myocytes, smooth muscle and endothelial cells. CONCLUSION: G-CSF treatment could be benefical to the regeneration of infarcted myocardium and significantly reduce scar size and it could be used for therapeutic intervention of the acute myocardial infarction.     

Expression of endostatin in ischemic myocardium of myocardial infarction rats

AIM: To study the expression of endostatin in ischemic myocardium of myocardial infarction (MI) rats in various periods and the correlation with VEGF expression and microvascular density (MVD).METHODS: Thirty-two male Sprague-Dawley rats after myocardial infarction were randomly divided into 7, 14, 21 and 28 days group.The sham group was normal control group (eight rats in each group).The expression of endostatin, VEGF and MVD in ischemic myocardium were observed by immunohistochemistry.RESULTS: The expression of endostatin significantly increased in the ischemic myocardium after MI, peaked at 7 days, then gradually decreased at 14, 21 and 28 days.The endostatin level at 28 days was the same as the shams.The changing trends of expression of endostatin in ischemic myocardium after MI were similar to that of VEGF and were significantly correlated with the MVD.CONCLUSION: The expression of endostatin increased in ischemic myocardium of myocardial infarction rats.The changing trends of endostatin were similar to that of VEGF and positively correlated with the MVD.These data suggest that endostatin may modulate ischemic myocardium angiogenesis after myocardial infarction.     

Influence of chronic stress on vasoactive substances and inflammatory factor in rat model with acute myocardial infarction by factorial analysis

AIM: To investigate the effect of chronic unpredictable mild stress(CUMS) on plasma endothelin, nitric oxide and interleukin-6, high-sensitivity C-reactive protein(hs-CRP) in rats after acute myocardial infarction(AMI).METHODS: After the rats of myocardial infarction(MI) were established, the animals were treated under the condition of CUMS for 4 weeks, then the contents of plasma(or serum) endothelin, nitric oxide, interleukin-6 and hs-CRP were measured and data were analyzed by two factor factorial analysis. RESULTS: The results of factorial analysis showed: MI alone had no significantly effect on the level of nitric oxide(P>0.05), but CUMS had significantly effect on increasing the level of nitric oxide(P<0.01). The CUMS had significantly interaction with MI on increasing the level of nitric oxide(P<0.01). Both MI and CUMS increased the level of hs-CRP(all P<0.01). However, no interaction was discovered between MI and CUMS(P>0.05). Both MI and CUMS had no effect on the level of ET-1 and IL-6(P>0.05).CONCLUSION: CUMS increases nitric oxide content and has cooperative effect with MI on increasing NO, both MI and CUMS significantly increase the level of CRP, but have no effect on the level of ET-1 or IL-6, suggesting that the abnormal increase in nitric oxide and hs-CRP contents may be the important pathophysiological changes of post-MI depression.     

Role of dendritic cells in myocardial infarction and cardiac remodeling

Myocardial infarction （MI） is one of the leading causes of death worldwide. One of the primary reasons is that the rupture of atherosclerotic plaque leads to the formation of thrombosis, and then interrupts the coronary blood flow, thus finally causing the death of myocardial cells and cardiac dysfunction. A large number of researches have revealed that dendritic cells （DCs） play an essential role in immune inflammatory responses in the occurrence and development of atherosclerosis and MI. This article reviews the role of DCs in atherosclerosis, myocardial ischemia/reperfusion injury and cardiac remodeling after MI, and shows the potential values of DCs as an immunotherapeutic strategy for MI.     

Alteration of local renin-angiotensin system of dogs with myocardial ischemia and external counterpulsation treatment

AIM:To examine the alteration of local renin-angiotensin system of dogs with myocardial ischemia and external counterpulsation treatment and its mechanism. METHODS:Acute myocardial ischemia was induced by occluding the LAD of ischemic and ECP groups. The tissue renin activity and angiotensin(AngⅡ) level in ischemic myocardium and aorta were measured. The expression of angiotensinogen and renin mRNA were detected by RT-PCR. RESULTS:Renin activity, AngⅡ level in ischemic myocardium and AngⅡ level in aorta of ECP group were lower than those of MI group. Except for renin in ischemic myocardium, angiotensinogen mRNA and renin in ischemic myocardium and angiotensinogen mRNA in aorta of ECP group were reduced to normal level. CONCLUSION:The inhibitory effect of ECP on cardiovascular renin activity and angiotensinogen gene expression could be one of the mechanisms by which ECP protects ischemic myocardium.     

Effects of diabetes on the development of heart failure in streptozotocin-induced diabetic rat model with acute myocardial infarction

AIM: To evaluate the time course and effect of diabetes on the development of heart failure (HF) in poorly controlled streptozotocin (STZ) -induced diabetic rat model for 70 d with acute myocardial infarction (AMI) in vivo. METHODS: All SD rats were randomized into four groups. Diabetes were induced by a single intraperitoneal injection of STZ (65 mg/kg), and 70 d later after the induction, AMI models were made with the ligation of left anterior descending coronary artery. The time course of diabetic effects on the development of heart failure in rats before and after AMI was observed. The survival rate of the rats and ultrastructure change of myocardium, the hemodynamics, the extent of the myocardial fibrosis, and the cardiac hypertrophy were also determined. RESULTS: After the ligation of left anterior descending coronary artery, the diabetic rats showed worse LV function and accelerated left ventricular (LV) remodeling compared with the non-diabetic ones. Myocardial fibrosis in both diabetic and non-diabetic rats subjected to AMI was similar in the early phase, while it was quite different after 1 month. CONCLUSION: Heart failure progression is accelerated in diabetic rat with AMI.