Acute Myocardial Injury In Rats Research Articles

Combined Bisoprolol and Trimetazidine ameliorate Arsenic trioxide -Induced Acute Myocardial Injury in Rats: Targeting PI3K/GSK-3β/Nrf2/HO-1 and NF-κB/iNOS Signaling Pathways, Inflammatory Mediators and Apoptosis

Background Arsenic-trioxide (ATO) is an effective therapy for acute promyelocytic leukemia. Unfortunately, its utility is hindered by the risk of myocardial injury. Both bisoprolol (BIS) and trimetazidine (TMZ) have various pharmacological features, including anti-oxidant, anti-inflammatory, and anti-apoptotic properties. Aim The cardioprotective effects of BIS and TMZ were studied, and their mechanistic role in ameliorating ATO-induced myocardial injury. Materials and Methods Forty male Wistar rats were randomly allotted into five groups as follows: normal control group (received normal saline, orally), ATO group (7.5 mg/kg, orally), BIS (8 mg/kg, orally), TMZ (60 mg/kg, orally), and finally combination group (BIS + TMZ + ATO). Following 21 days, samples of serum and cardiac tissues were obtained to perform biochemical, molecular, and histopathological investigations. Results The present study showed that ATO caused myocardial injury evidenced by changes in serum biomarkers (Aspatate aminotransferase, alanine aminotransferase, alkaline phosphatase, lactate dehydrogenase, creatine kinase-MB, and cardiac troponin-1), electrolyte imbalance, and lipid profiles alongside histopathologic changes. In addition, ATO administration significantly elevated malondialdehyde, nicotinamide adenine dinucleotide phosphate hydrogen oxidase, myloperoxidase, total nitrite, inducible nitric oxide synthase, tumor necrosis factor-alpha, interleukin-1β, interleukin-6, 8-Hydroxy-2'-deoxyguanosine, nuclear factor NF-kappa-B p65 subunit, glycogen synthase kinase-3 beta, and caspase-3 expression contemporaneously with down-regulation of reduced glutathione, glutathione peroxidase, superoxide dismutase, catalase, heme oxygenase 1, nuclear factor erythroid 2–related factor 2, phosphatidylinositol-3 kinase, p-PI3K, and Bcl-2 expression. Interestingly, pre-treatment with BIS and TMZ significantly reversed the detrimental effects of ATO-induced myocardial injury at both cellular and molecular levels. Otherwise, combining the two drugs displayed more enhancement than each drug alone. Conclusion The present research depicted that BIS and TMZ have the potential to protect the heart and provide therapeutic benefits by preventing acute heart injury induced by ATO. This is achieved by reversing the redox-sensitive pathway, reducing inflammation, and inhibiting apoptosis.

The Cardioprotective Effect of Corosolic Acid in the Diabetic Rats: A Possible Mechanism of the PPAR-γ Pathway.

The study was conducted to determine whether corosolic acid could protect the myocardium of diabetic rats from damage caused by isoproterenol (ISO) and, if so, how peroxisome proliferator-activated receptor gamma (PPAR-γ) activation might contribute into this protection. Diabetes in the rats was induced by streptozotocin (STZ), and it was divided into four groups: the diabetic control group, diabetic rats treated with corosolic acid, diabetic rats treated with GW9662, and diabetic rats treated with corosolic acid plus GW9662. The study was carried out for 28 days. The diabetic control and ISO control groups showed a decrease in mean arterial pressure (MAP) and diastolic arterial pressure (DAP) and an increase in systolic arterial pressure (SAP). The rat myocardium was activated by corosolic acid treatment, which elevated PPAR-γ expression. A histopathological analysis showed a significant reduction in myocardial damage by reducing myonecrosis and edema. It was found that myocardial levels of CK-MB and LDH levels were significantly increased after treatment with corosolic acid. By decreasing lipid peroxidation and increasing endogenous antioxidant levels, corosolic acid therapy showed a significant improvement over the ISO diabetic group. In conclusion, our results prove that corosolic acid can ameliorate ISO-induced acute myocardial injury in rats. Based on these results, corosolic acid seems to be a viable new target for the treatment of cardiovascular diseases and other diseases of a similar nature.

Cardioprotection of cortistatin against isoproterenol-induced myocardial injury in rats.

BackgroundThe present study was designed to examine whether cortistatin (CORT) could protect rats from myocardial injury induced by subcutaneously injecting isoproterenol (ISO) and to clarify the possible mechanisms.MethodsMale Sprague-Dawley (SD) rats were placed at random into four groups: the control group, the ISO group, the ISO + CORT 25 µg/(kg·d) group, and the ISO + CORT 50 µg/(kg·d) group. Rat models of myocardial injury were established with the subcutaneous (s.c.) injections of 85 mg/kg ISO for 2 days. In the ISO+ CORT 25 µg/(kg·d) group and ISO+ CORT 50 µg/(kg·d) group, rats were given s.c. injections of CORT 25 µg/(kg·d) and CORT 50 µg/(kg·d) on the day before ISO, 3 days, respectively. Serum malondialdehyde (MDA) content, lactate dehydrogenase (LDH) activity, and creatine kinase isoenzyme (CK-MB) activity were measured by corresponding test kits. Western blot was applied to evaluate the expression of endoplasmic reticulum stress-related protein glucose regulatory protein 78 (GRP78), enhancer-binding protein homologous protein (CHOP), cysteinyl aspartate specific proteinase-12 (caspase-12), LC3-II, Beclin-1, and p62 in the rat myocardium.ResultsCORT alleviated the increased enzyme activities of serum LDH and CK-MB, and content of MDA (a typical marker of lipid peroxidation) in rats induced by ISO. CORT also prevented pathological myocardial injury in rats induced by ISO. Moreover, CORT attenuated the increased protein levels of GRP78, CHOP, and caspase-12, and reduced the increase of LC3-II, LC3-II/I, Beclin-1, and p62 in rats induced by ISO.ConclusionsThese data demonstrate that CORT can attenuate ISO-induced acute myocardial injury in rats likely by reducing lipid peroxidation, and inhibiting endoplasmic reticulum stress and autophagy. This supports CORT as a potentially being a new target for preventing and treating myocardial injury and its related disease.

Rosuvastatin and retinoic acid may act as ‘pleiotropic agents’ against β-adrenergic agonist-induced acute myocardial injury through modulation of multiple signalling pathways

Cardiovascular disorders constitute the principal cause of deaths worldwide and will continue as the major disease-burden by the year 2060. A significant proportion of heart failures occur because of use and misuse of drugs and most of the investigational agents fail to achieve any clinical relevance. Here, we investigated rosuvastatin and retinoic acid for their “pharmacological pleiotropy” against high dose β-adrenergic agonist (isoproterenol)-induced acute myocardial insult. Rats were pretreated with rosuvastatin and/or retinoic acid for seven days and the myocardial injury was induced by administering isoproterenol on the seventh and eighth day. After induction, rats were anaesthetized for electrocardiography, then sacrificed and different samples were collected/stored for various downstream assays. Myocardial injury with isoproterenol resulted in increased cardiac mass, decreased R-wave amplitude, increased QRS and QT durations; elevated levels of cardiac markers like cTnI, CK-MB, ALT and AST; increased lipid peroxidation, protein carbonylation and tissue nitric oxide levels; decreased endogenous antioxidants like SOD, CAT, GR, GST, GPx and total antioxidant activity; increased inflammatory markers like TNF-α and IL-6; decreased the mRNA expression of Nrf2 and Bcl-2; increased the mRNA expression of Bax, eNOS and iNOS genes. Pretreatment with rosuvastatin and/or retinoic acid mitigated many of the above biochemical and pathological alterations. Our results demonstrate that rosuvastatin and retinoic acid exert cardioprotective effects and may act as potential agents in the prevention of β-adrenergic agonist-induced acute myocardial injury in rats. Cardioprotective potential of rosuvastatin and retinoic acid could be attributed to their influence on the redox pathways, immunomodulation, membrane stability, Nrf2 preservation, iNOS and Bax expression levels. Thus, they may act directly or indirectly at various steps, the breakpoints, in the pathophysiological cascade responsible for cardiac injury. Our study gives insights about the pharmacological pleiotropism of rosuvastatin and retinoic acid.

CD90+ cardiac fibroblasts reduce fibrosis of acute myocardial injury in rats.

To explore the differentiation tendency of CD90+ cardiac fibroblast (CFs) into cardiomyogenic cells in vitro and repair functions in acute myocardial infarction rats. CD90+ subpopulation was sorted from rat CFs by flow cytometry. 10 μmoL/L of 5-Azacytosine (5-aza) was used to induce differentiation of CFs into cardiomyogenic cells. An acute myocardial infarction model was prepared by ligation of the rat left anterior descending coronary artery. After nuclei were labeled by DAPI, induced CD90+ CFs were injected into the infarction marginal zone. Before coronary ligation, 40 min after ligation, and at 7 and 14 days after cell transplantation, cardiac function changes were detected by ultrasound imaging system respectively. cTnT and endothelial cell marker VIII factor were detected by immunofluorescence staining. Infarct size was examined by TTC staining. Fibrosis was evaluated with masson's trichrome staining, vimentin, type I and type III collagen staining. CD90+ CFs sorted by flow cytometry was 34.9%. On day 28 after induction, the cTnT positive rate was 61.17 ± 9.75%. Left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS) at days 7 and 14 after transplantation were significantly increased compared with those before transplantation (P < 0.05). LVEF and LVFS at the 14th day after transplantation were also significantly increased compared with those at the 7th day (LVEF: 61.40 ± 2.45% vs. 56.25 ± 2.9%, LVFS: 33.21 ± 0.68% vs. 30.26 ± 2.06%, P < 0.01). Additionally, small numbers of CD90+ CFs differentiated into cardiomyocytes and became involved in neovascularization. CD90+ CFs and CFs reduced myocardial infarct size at days 14. It was significantly smaller in rats with CFs transplantation group than those in MI group(24.78 ± 2.28% vs. 31.28 ± 2.83%, P < 0.05), and it was also significantly smaller in rats with CD90+CFs transplantation group than those in CFs transplantation group (17.47 ± 4.15% vs. 24.78 ± 2.28%, P < 0.05). Meanwhile, The percentage of fibrotic area and vimentin, type I and type III collagen in the infarct border zone and infarct area were both significantly reduced in CD90 + CFs. CD90+ CFs is the preponderant subpopulation of cardiomyogenic differentiation, with potential use as seed cells in basic and clinical research of heart regeneration and repair.

Molecular and biochemical evidence on the protective effects of quercetin in isoproterenol-induced acute myocardial injury in rats.

Cardioprotection represents one of the most important and realistic aspects of preventive therapy today. Quercetin, a naturally occurring dietary flavone, has been studied extensively for its antioxidant properties. The objective of present study is to find out the cardioprotective activity and to explore the underlying mechanisms of quercetin pretreatment (50 mg/kg body weight, orally) for 14 days against isoproterenol (ISO; 100 mg/kg body weight, subcutaneously) induced myocardial infarction in Wistar rats. Cardiac diagnostic markers, oxidative stress, inflammatory cytokines, histopathology along with gene expression analysis of calpain 1 and 2 were carried out in experimental rats. Quercetin pretreatment showed protective effects on heart by significantly attenuating the ISO-induced oxidative stress, inflammation, protecting heart architecture, and by downregulation of the expression of calpain. Overall, these findings revealed the cardio-protective potential of quercetin and its mechanism of action against ISO-induced MI in rats.

Molecular and biochemical evidence on the protective effects of embelin and carnosic acid in isoproterenol-induced acute myocardial injury in rats

AimsAcute myocardial infarction is a serious acute cardiac disorder and heart disease is still a major public health problem in adults. We investigated the effects of embelin (EMB) and carnosic acid (CA) in animals with isoproterenol (ISO)-induced myocardial injury. Main methodsAdult male Wistar–Albino rats were divided into four groups: control, ISO, ISO with EMB, and ISO with CA. Before myocardial injury was induced, drugs were administered by oral gavage. Myocardial injury was induced by subcutaneous injection of ISO hydrochloride for 2 consecutive days. Serum cardiac troponin I (cTnI), ischemia modified albumin (IMA), heart fatty acid binding protein (HFABP) levels and paraoxonase-1 (PON-1) activity, tissue total oxidant status (TOS), total antioxidant status (TAS), total thiol (TT), tumor necrosis factor-α (TNF-α) levels, superoxide dismutase (SOD) activity, and glutathione peroxidase (GSH-Px) activity were measured. Tissue mRNA expression levels of nuclear factor-kappa B (NF-κB), P38 mitogen-activated protein kinase (p38 MAPK), and nuclear factor erythroid 2-related factor 2 (Nrf2) were analyzed. In addition, cardiac tissues were evaluated histopathologically and immunohistochemically. Key findingsAll tested compounds reduced myocardial damage, apoptosis, cTnI, IMA, HFABP, TOS, and TNF-α levels, NF-κB, p38 MAPK, and phosphorylated c-Jun N-terminal protein kinase (pJNK 1/2) expressions. All tested compounds increased SOD activity, GSH-Px activity, TAS levels, TT levels, phosphorylated extracellular signal-regulated kinase (pERK 1/2), and Nrf2 expressions. SignificanceOur results suggest that EMB and CA pretreatment could reduce myocardial injury via antiinflammatory, antioxidant, and antiapoptotic effects.

Puerarin attenuates severe burn-induced acute myocardial injury in rats

BackgroundPuerarin, the main isoflavone glycoside extracted from the root of Pueraria lobata, is widely prescribed for patients with cardiovascular disorders in China. This study investigates the effect of puerarin on severe burn-induced acute myocardial injury in rats and its underlying mechanisms. Materials and methodsHealthy adult Wistar rats were divided into three groups: (1) sham group, sham burn treatment; (2) burn group, third-degree burns over 30% of the total body surface area (TBSA) with lactated Ringer's solution for resuscitation; and (3) burn plus puerarin group, third-degree burns over 30% of TBSA with lactated Ringer's solution containing puerarin for resuscitation. The burned animals were sacrificed at 1, 3, 6, 12, and 24h after burn injury. Myocardial injury was evaluated by analyzing serum creatine kinase MB fraction (CK-MB) activity and cardiac troponin T (cTNT) level. Changes in cardiomyocyte ultrastructure were also determined using a transmission electron microscope. Tumor necrosis factor (TNF)-α concentration in serum was measured by radioimmunoassay. Cardiac myeloperoxidase (MPO) activity and malondialdehyde (MDA) concentration were measured to determine neutrophil infiltration and oxidative stress in the heart, respectively. The expression of p38 mitogen-activated protein (MAP) kinase in the heart was determined by Western blot analysis. ResultsAfter the 30% TBSA full-thickness burn injury, serum CK-MB activities and cTnT levels increased markedly, both of which were significantly decreased by the puerarin treatment. The level of serum TNF-α concentration in burn group at each time-point was obviously higher than those in sham group (1.09±0.09ng/ml), and it reached the peak value at 12h post burn. Burn trauma also resulted in worsen ultrastructural condition, elevated MPO activity and MDA content in heart tissue, and a significant activation of cardiac p38 MAP kinase. Administration of puerarin improved the ultrastructural changes in cardiomyocytes, decreased TNF-α concentration in serum as well as suppressed cardiac MPO activity and reduced MDA content, and abolished the activation of p38 MAP kinase in heart tissue after severe burn. ConclusionsThese results suggest that puerarin attenuates inflammatory responses, reduces neutrophil infiltration and oxidative stress in the heart, and protects against acute myocardial injury induced by severe burn.

Regulation of signal transducer and activator of transcription 3 and apoptotic pathways by betaine attenuates isoproterenol-induced acute myocardial injury in rats.

The present study was designed to investigate the cardioprotective effects of betaine on acute myocardial ischemia induced experimentally in rats focusing on regulation of signal transducer and activator of transcription 3 (STAT3) and apoptotic pathways as the potential mechanism underlying the drug effect. Male Sprague Dawley rats were treated with betaine (100, 200, and 400 mg/kg) orally for 40 days. Acute myocardial ischemic injury was induced in rats by subcutaneous injection of isoproterenol (85 mg/kg), for two consecutive days. Serum cardiac marker enzyme, histopathological variables and expression of protein levels were analyzed. Oral administration of betaine (200 and 400 mg/kg) significantly reduced the level of cardiac marker enzyme in the serum and prevented left ventricular remodeling. Western blot analysis showed that isoproterenol-induced phosphorylation of STAT3 was maintained or further enhanced by betaine treatment in myocardium. Furthermore, betaine (200 and 400 mg/kg) treatment increased the ventricular expression of Bcl-2 and reduced the level of Bax, therefore causing a significant increase in the ratio of Bcl-2/Bax. The protective role of betaine on myocardial damage was further confirmed by histopathological examination. In summary, our results showed that betaine pretreatment attenuated isoproterenol-induced acute myocardial ischemia via the regulation of STAT3 and apoptotic pathways.

Regulation of endothelial nitric oxide synthase and asymmetric dimethylarginine by matrine attenuates isoproterenol-induced acute myocardial injury in rats

This study was designed to investigate the cardioprotective effects of matrine on regulation of endothelial nitric oxide synthase (eNOS) and asymmetric dimethylarginine (ADMA) in isoproterenol-induced acute myocardial ischaemic rats. Male Sprague-Dawley rats were pretreated with matrine (200, 100 and 50 mg/kg) orally for 10 days. Acute myocardial injury was induced in rats by subcutaneous injection of isoproterenol. Serum and haemodynamic parameters, histopathological variables and expression of protein levels were analysed. Oral administration of matrine (200, 100 and 50 mg/kg) significantly attenuated isoproterenol-induced cardiac necrosis and left ventricular dysfunction. Matrine treatment restored impaired ventricular Akt and eNOS protein expression with concomitant increased phosphorylation of Akt (Ser473) and eNOS (Ser1177), and also restored glycogen synthase kinase 3β activity, as indicated by increased phosphorylation at Ser 9. Moreover, treatment with matrine had no effect on the isoproterenol-induced elevated protein arginine methyltransferase 1 protein expression, but could significantly normalize the reduced dimethylarginine dimethylaminohydrolase 2 expression and attenuate the increased serum level of ADMA. The expression of catechol-o-methyltransferase and monoamine oxidase did not differ among all groups (all P > 0.05). Our results suggested that matrine protects against isoproterenol-induced myocardial ischaemia via eNOS and ADMA pathway.

Effects of Inula Britannica on myocardial caspase-3 and cytochrome C expression following overtraining-induced acute myocardial injury in rats

Objective To investigate the effects of Inula Britannica on myocardial caspase-3 and cytochrome c ( cyt c) following overtraining-induced acute myocardial injury in rats.Methods Forty-eight male Wistar rats weighing 200-220 g were randomly divided into 3 groups:group control (group C,n =8) ; group exhausting swim (group E,n =24) and group Inula Britannica (group IB,n =16).The animal model of overtraining-indnced acute myocardial injury was developed by exhausting swim.The animals were forced to swim until they were exhausted.The animals sank to the bottom and no righting reflex or escape response was elicited when they were taken out of water in groups E and IB.In group IB oral Inula Britannica 25 ml/kg was given 24 h and immediately before overtraining.Blood samples were taken from inferior vena cava immediately and at 6,24 h after overtraining in group E and at 6,24 h after overtraining in group IB for determination of serum cardiac troponin I (cTnI) concentration (by ELISA).The animals were sacrificed after blood sampling and myocardial specimens were obtained for microscopic examination and determination of caspase-3 and cyt c expression (by immuno-histochemistry).Results Overtraining significantly increased serum cTnI concentration and up-regulated myocardial caspase-3 and cyt c expression in group E as compared with group C.Oral Inula Britannica significantly attenuated overtraining-induced increase in serum cTnI concentration and myocardial caspase-3 and cyt c expression in group IB as compared with group E.Conclusion Inula Britannica can reduce overtraining-induced acute myocardial injury by down-regulating caspase-3 and cyt c expression. Key words: Inula; Hyperkinesis; Cardiomyopathies; Cytochromes c; Caspase 3

Pro-apoptotic role of nuclear factor-κB in adriamycin-induced acute myocardial injury in rats

Nuclear factor κB (NF-κB) is activated by a wide range of inducers and is able to mediate gene transcription. We investigated the role of NF-κB in adriamycin-induced myocardial injury in rats and its mechanism of action. A total of 30 male Wistar rats were randomly divided into 3 groups: control, anthracycline antibiotic adriamycin (ADR) and ADR + pyrrolidine dithiocarbamate (PDTC). Myocardial apoptosis was detected by TUNEL assay; myocardium p53 gene expression was examined by RT-PCR analysis; location and distribution of p53 was observed by immunohistochemical assay; myocardial expression of p53 protein was assessed by Western blot analysis and activity of NF-κB was evaluated by electrophoretic mobility shift assay. The binding activity of NF-κB, myocardial apoptotic index and expression of p53 increased significantly in the ADR groups. All of these changes induced by ADR were inhibited by PDTC. It was concluded that NF-κB activation may be pro-apoptotic through regulation of the expression of p53 in adriamycin-induced myocardial injury.

Effects of Buzhong Yiqi decoction on adriamycin induced heart failure in rats

To study the effects and mechanism of Buzhong Yiqi decoction on adriamycin-induced acute myocardial injury in rats. 50 rats were randomly divided to five groups: control group, heart failure group, low dose Buzhong Yiqi decoction, high dose Buzhong Yiqi decoction and captopril group. Adriamycin was injected into the latter four groups to built a model of heart failure. Then, the effects of different doses of Buzhong Yiqi decoction on hemodynamics, cardiac tissue histological changes, antioxidant capacity and apoptosis of the damaged hearts were studied. Adriamycin led to myocardial fiber swelling and fracture, Buzhong Yiqi decoction could reduce myocardial lesions. Buzhong Yiqi decoction could also improve heart antioxidant capacity and inhibit adriamycin-induced cardiomyocyte apoptosis. Buzhong Yiqi decoction could significantly ease adriamycin induced heart failure in rats, and the mechanism is related to anti-oxidation and inhibiting apoptosis.

Myocardial post-conditioning with Danshen-Gegen decoction protects against isoproterenol-induced myocardial injury via a PKCε/mKATP-mediated pathway in rats

BackgroundDanshen-Gegen decoction (DG), a Chinese herbal formula, has been demonstrated to be effective for the treatment of coronary heart disease such as myocardial infarction. In the present study, we investigated the effect of DG post-conditioning on isoproterenol (ISO)-induced myocardial injury in rats.MethodsISO was injected intraperitoneally (200 mg/kg) to induce acute (2-6 hours) myocardial injury in adult female rats. DG (4 g/kg) was administered per oral immediately after the injection of ISO in the rats. Extent of myocardial injury was assessed by measurements of plasma enzyme activities. Myocardial mitochondrial glutathione antioxidant status, lipid peroxidation and mitochondrial calcium ion loading and cytochrome c release were also measured. Effects of inhibitors of protein kinase C-epsilon (PKCε) ranslocation and mitochondrial ATP-sensitive potassium channel (mKATP) on myocardial post-conditioning by DG were investigated.ResultsISO inflicted acute myocardial injury in the rats as evidenced by increased plasma enzyme activities. DG post-treatment alleviated the ISO-induced acute myocardial injury.ConclusionDG post-treatment protected the myocardium against ISO-induced acute injury in rats. The myocardial post-conditioning by DG is likely mediated by PKCε/mKATP signaling pathway.

Abnormal Immunostaining for Dystrophin in Isoproterenol-induced Acute Myocardial Injury in Rats: Evidence for Change in Dystrophin in the Absence of Genetic Defect

Abnormalities in the gene for Duchenne muscular dystrophy produce skeletal and myocardial changes, by impairing dystrophin production in patients with Duchenne and Becker muscular dystrophy. However, it is not known whether myocardial dystrophin may be altered in patients with other heart diseases. To investigate whether changes in myocardial dystrophin may be induced by acute myocardial injury, the immunostaining patterns of myocardial dystrophin were examined, together with those of myocardial actin, in rats with isoproterenol-induced myocardial damage. Hearts were excised at 6, 12, 24 and 48 h, and 1 and 4 weeks after the subcutaneous administration of 100 mg/kg of isoproterenol. Frozen serial sections were prepared for haematoxylin and eosin staining, and for immunostaining for dystrophin and actin. The immunostaining patterns of actin were used as an indicator of cell injury. The myocardial cells observed were classified into four types, according to staining pattern: normal for both actin and dystrophin (Type 1); normal for actin, but abnormal for dystrophin (Type 2); abnormal for actin, but normal for dystrophin (Type 3); and abnormal for both actin and dsytrophin (Type 4). The percentage of myocardial cells with abnormal staining (Types 2, 3 and 4) at 6, 12, 24 and 48 h after isoproterenol injection was 22.4, 12.6, 16.0 and 2.4%, respectively; most cells were Types 3 and 4. One week after injection or later, no Type 3 or 4 cells were detected, while the percentages of Type 2 cells were 2.7% for 1 week and 2.2% for 4 weeks, significantly higher than the corresponding value in the control group. In conclusion, changes in myocardial dystrophin may occur in isoproterenol-induced myocardial injury in rats.