The effects of mebudipine on myocardial arrhythmia induced by ischemia-reperfusion injury in isolated rat heart.

Reperfusion of the heart after an ischemic insult may lead to potentially lethal arrhythmias and cardimyocyte cell death via apoptosis and necrosis. In addition, previous studies showed that calcium channel blockers may have a protective role in the myocardium against arrhythmia and irreversible tissue injury. Therefore, this study was aimed to investigate the effects of mebudipine on myocardial arrhythmias and tissue injury induced by ischemia/reperfusion injury in isolated rat hearts. Male Wistar rats (250­300g) were randomly divided to Sham group (without ischemia), control group (ischemia without drug), drug group (ischemia with mebudipine 0.1nM) and vehicle group (ischemia with ethanol 0.01%). The hearts of anaesthetized rats were removed and mounted on Langendorff apparatus and perfused by Krebs­Henseleit solution under constant pressure of 75 mmHg at 37°C. Impulsive heart rate was monitored with bipolar golden electrodes. The electrocardiographs were recorded throughout the experiment and interpreted using the Lambeth convention. LDH and CPK activities in coronary effluent were analyzed spectrophotometrically. Hematoxilin & Eosin staining was performed for evaluation of microscopic architecture of the myocardium and tissue injury.  Pretreatment with mebudipine significantly decreased the number of ventricular premature beats (VPB) as compared with control group. The similar findings were seen in the number of ventricular tachycardia (VT) and fibrillation (VF) among groups. In addition, mebudipine significantly reduced the severity of arrhythmias in comparison with control hearts.  Moreover, the drug group demonstrated marked improvement in edema and infiltration of inflammatory cells especially with regard to the degree of myonecrosis and cell lysis.Mebudipine diminished the number and the incidence of myocardial arrhythmias induced by reperfusion injury and the severity of tissue injury.

Preventive effects of garlic (Allium sativum) on oxidative stress and histopathology of cardiac tissue in streptozotocin-induced diabetic rats.

Since some complications of diabetes mellitus may be caused or exacerbated by an oxidative stress, the protective effects of garlic (Allium sativum) were investigated in the blood and heart of streptozotocin-induced diabetic rats. Twenty-eight male Wistar rats were randomly divided into four groups: control, garlic, diabetic, and diabetic+garlic. Diabetes was induced by intraperitoneal (i.p.) injection of streptozotocin (50 mg/kg) in male rats. Rats were fed with raw fresh garlic homogenate (250 mg/kg) six days a week by gavage for a period of 6 weeks. At the end of the 6th week blood samples and heart tissues were collected and used for determination of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and histological evaluation. Induction of diabetes increased MDA levels in blood and homogenates of heart. In diabetic rats treated with garlic, MDA levels decreased in blood and heart homogenates. Treatment of diabetic rats with garlic increased SOD, GPX and CAT in blood and heart homogenates. Histopathological finding of the myocardial tissue confirmed a protective role for garlic in diabetic rats. Thus, the present study reveals that garlic may effectively modulate antioxidants status in the blood and heart of streptozotocin induced-diabetic rats.

Diosgenin-induced protection against myocardial ischaemia-reperfusion injury is mediated by mitochondrial KATP channels in a rat model.

OBJECTIVE: This study was aimed to evaluate the effects of diosgenin on myocardial ischaemia-reperfusion injury and the potential involvement of mitochondrial KATP (mitoKATP) channel and nitric oxide (NO) system blockades in this field. MATERIALS AND METHODS: After isolation of hearts of male Wister rats, the study was conducted on control and diosgenin- receiving hearts in the presence or absence of 5-HD and L-NAME (as antagonists of mitoKATP channel and NO system, respectively) in an isolated buffer-perfused heart model. Global ischaemia was induced by 30-min occlusion of aortic flow followed by 90-min reperfusion. Cardiac haemodynamics were recorded throughout the experiment using a PowerLab data acquisition system. RESULTS: The levels of creatine kinase (CK-MB) and lactate dehydrogenase (LDH) in the coronary effluents were estimated colourimetrically. Diosgenin pre-administration significantly decreased the release of LDH and CK-MD into the coronary effluent as compared the with the control group (P < 0.05). The left ventricular developed pressure (LVDP) and contractility (± dP/dt) were significantly improved and restored to pre-ischaemic values in the diosgenin-receiving group (P < 0.05). There were no significant differences in left ventricular end-diastolic pressure, coronary flow and heart rate between the control and diosgenin-treated groups during the pre-ischaemic and reperfusion periods. Blocking the mitoKATP channels by 5-HD completely eliminated the positive effect of the diosgenin on the LVDP and ± dP/dt (P < 0.05). However, blocking the NO system by L-NAME slightly reduced the diosgenin effects and the inhibitory effect of L-NAME was less than 5-HD. CONCLUSION: The results showed that diosgenin may have cardioprotective effects against myocardial reperfusion injury through activating the mitoKATP channels.

The effects of Ramadan fasting on endothelial function in patients with cardiovascular diseases.

BACKGROUND/OBJECTIVES: Endothelial dysfunction, which can be manifested by loss of nitric oxide bioavailability, is an increasingly recognized cause of cardiovascular diseases. Previous studies showed that diets affect endothelial function and modify cardiovascular risks. This study aimed to assess the effects of Ramadan fasting, as a diet intervention, on endothelial function. SUBJECTS/METHODS: The study population consisted of 21 male patients (mean age: 52±9 years) with cardiovascular risks (coronary artery disease, cerebrovascular or peripheral arterial diseases). The biochemical variables in serum of patients were measured 2 days before and after Ramadan fasting. The levels of asymmetric dimethylarginine (ADMA) and vascular endothelial growth factor (VEGF) were evaluated using the enzyme-linked immunosorbent assay. Nitric oxide (NO) and Malondialdehyde (MDA) levels were measured by the Griess and thiobarbituric acid reaction substances assay, respectively. RESULTS: NO levels in patients after Ramadan fasting were significantly higher compared with the baseline value (85.1±11.54 vs 75.8±10.7 µmol/l) (P<0.05). Post-Ramadan levels of ADMA decreased significantly in comparison with pre-Ramadan levels (802.6±60.9 vs 837.6±51.0 nmol/l) (P<0.05). In addition, the levels of VEGF and MDA changed during Ramadan fasting, but these changes were not statistically significant (228.1±27.1 vs 222.7±22.9 pg/ml and 3.2±0.7 vs 3.6±1.1 µmol/l, respectively). CONCLUSIONS: Ramadan fasting may have beneficial effects on endothelial function and can modulate cardiovascular risks. Further studies are needed to confirm the clinical significance of Ramadan fasting on cardiovascular health.

The effect of mebudipine on cardiac function and activity of the myocardial nitric oxide system in ischaemia-reperfusion injury in rats.

OBJECTIVES: Previous studies have suggested that failure of the synthesis of nitric oxide is involved in the pathophysiology of myocardial ischaemia-reperfusion injury. In this study, we investigated the effect of mebudipine, a new dihydropyridine calcium channel blocker, on cardiac function and activity of the myocardial nitric oxide system in ischaemia-reperfusion injury in isolated rat hearts. METHODS: Forty male Wistar rats (250-300 g) were divided into four groups (n = 10): sham, control, vehicle and drug groups. The animals were anesthetised with sodium pentobarbital (6 mg/kg intraperitoneal). The hearts were quickly removed, mounted on a Longendorff apparatus and perfused with Krebs-Henseleit solution under constant pressure at 37°C. After 20 min stabilisation period, the ischaemic groups received 30 min global ischaemia and 120 min reperfusion. For the drug and vehicle groups, before ischaemia the hearts were perfused with mebudipine (10(-3) µM) or ethanol-enriched solution (0.01%) for 25 min, respectively. Myocardial function, and creatine kinase, lactate dehydrogenase and total nitric oxide metabolite (nitrite and nitrate) levels were analysed. RESULTS: Cardiac functions had recovered significantly in the mebudipine group (p < 0.01). Furthermore, mebudipine remarkably reduced the levels of lactate dehydrogenase and creatine kinase in the coronary effluent and increased myocardial nitric oxide metabolite levels compared with the control group. CONCLUSION: Our results indicate that mebudipine reduced the intensity of myocardial ischaemia-reperfusion injury, and that activation of the myocardial nitric oxide system played an important role in this regard.