The dose-dependent effect of chronic Verapamil treatment on cardiac function in isolated rat heart with Hypertension

Funding Acknowledgements

Type of funding sources: None.

Introduction

Verapamil, a calcium channel blocker, is used for treatment of hypertension, paroxysmal supraventricular tachycardia  and angina pectoris. It primarily blocks L-type calcium channels preventing excessive influx of calcium into cardiomyocytes, leading to negative inotropic effect, and smooth muscle cells resulting in reduced relaxation of vasculature. With calcium antagonism it also causes negative chronotropic effect. However, there is no data on it’s dose-dependent effects on cardiac dynamic parameters and heart rate on isolated rat heart with hypertension.

Purpose

To investigate chronic, dose-dependent effects of Verapamil on cardiodynamic parameters in isolated rat heart with hypertension.

Methods

The present 4-week study was carried out on 24 spontaneously hypertensive Wistar Kyoto male rats  (6 weeks old): Control (n = 6), rats treated with 0.5 mg/kg/day of Verapamil (n = 6), rats treated with 5 mg/kg/day of Verapamil (n = 6) and rats treated with 50 mg/kg/day of Verapamil (n = 6). Isolated rat hearts were perfused on Langendorff perfusion apparatus.

Results

Chronic, low-dose Verapamil treatment significantly depressed function of all cardiodynamic parameters of the hypertensive heart when compared to the rats treated with higher doses of Verapamil (p < 0.001), except on the coronary flow and heart rate when compared to the Control (p= 0.137; p = 1.000, respectively). There was no significant differences between Verapamil in middle dose (5 mg/kg/day) and the Control group in inotropic (p = 0.415) and lusitropic (p = 1.000) effects, while it significantly lowered values of coronary flow (p = 0.002). It achieved significantly lower inotropic, lusitropic and chronotropic effects (p < 0.001) than high Verapamil dose and significantly better inotropic (p = 0.017), lusitropic (p < 0.001), but not chronotropic effects than low-dose Verapamil treatment (p = 0.179). High-dose, chronic treatment with Verapamil significantly intensified function of  the isolated rat heart with hypertension when compared to Control and lower doses of Verapamil (p < 0.001), without significant effects on coronary flow (p = 0.363).

Conclusions

Chronic treatment with Verapamil in high dose achieved better inotropic, chronotropic and lusitropic effects than treatment in low and middle doses of Verapamil, without significant effects on coronary flow. There is dose-depended effect of chronic Verapamil treatment on cardiac function of isolated rat heart with hypertension.

P561Acute effects of dronedarone and amiodarone on functional, morphological and oxidative stress parameters in isolated rat heart with hypertension

Introduction

Amiodarone represents the most widely used antiarrhythmic drug, even though it has been shown that it has negative inotropic and lusitropic effect in healthy hears. On the other hand, dronedarone reduces the risk of recurrent atrial fibrillation, but with increased early mortality related to the worsening of heart failure. However, the mechanisms responsible for these fatal outcomes remain unclear and require further examinations. 

Purpose

To investigate acute, direct effects of Dronedarone and Amiodarone on cardiac contractility, coronary flow and oxidative stress parameters in isolated rat heart with hypertension.

Methods

 The present study was carried out on 18 isolated hearts of spontaneously hypertensive Wistar Kyoto male rats (6 weeks old, bodyweight 200 ± 10 g). After isolation, all hearts were retrogradely perfused according to Langendorff technique with a gradually increment of coronary perfusion pressure (CPP from 40 to 120 cm H2O) and randomly divided into 3 groups: Control (n = 6), Amiodarone (n = 6, isolated hearts perfused with Amiodarone in dose of 3 umol), Dronedarone (n = 6, isolated hearts perfused with Dronedarone in dose of 1.8 umol). During ex vivo protocol continuously were registered cardiac contractility parameters and coronary flow, while from collected coronary venous effluent markers of oxidative stress were measured. All hearts were then fixated and stained with Hematoxylin/eosin.

Results

 Dronedarone severely depressed the function of all cardiodynamic parameters of the heart compared with Amiodarone or Control while Amiodarone intensified the function of the isolated rat heart with hypertension compared to Control (dp/dt max mmHg/s at coronary perfusion pressure 120cmH2O Dronedarone vs. Amiodarone vs. Control 579.733 ± 202.27 vs. 3063.65 ± 467.93 vs. 2682.88 ± 368.75; p < 0.001. dp/dt min mmHg/s 120cmH2O -352.13 ± 204.65 vs. 1960 ± 242.21 vs. -1858.83 ± 118.23; p < 0.001. SLVP mmHg at CPP 120cmH20 27.8 ± 3.46 vs. 98.95 ± 11.78 vs. 71.45 ± 7.56; p < 0.001. DLVP mmHg at CPP 120cmH2O 6.32 ± 0.49 vs. 4.83 ± 0.54 vs. 0.85 ± 0.35; p < 0.001). Acute administration of Dronedarone decreased the level of NO2- and increased the level of H2O2 , while Amiodarone heightens O2- levels (O2- nmol/min g wt at coronary perfusion pressure 120cmH2O Dronedarone vs. Amiodarone vs. Control  28.62 ± 2.54 vs. 77.3 ± 8.86 vs. 31.72 ± 4.56; p < 0.001. H2O2 nmol/min g wt at CPP 120cmH2O 92.56 ± 11.65 vs. 48.63 ± 10.11 vs. 42.84 ± 84; p < 0.001. NO2- nmol/min g wt at CPP 120cmH2O 38.61 ± 4.94 vs.  82.28 ± 5.76 vs.  64.71 ± 3.51; p < 0.001). Pathohistological, structural changes were observed in both, experimental groups.

Conclusions

 Acute administration of Dronedarone depresses cardiac function in isolated, working rat heart with hypertension, with decreasing the NO2- levels, increasing the level of H2O2 and enhanced structural changes when compared to Amiodarone.

Inhibition of gasotransmitters production and calcium influx affect cardiodynamic variables and cardiac oxidative stress in propofol-anesthetized male Wistar rats

It has been assumed that the cardioprotective effects of propofol are due to its non-anesthetic pleiotropic cardiac and vasodilator effects, in which gasotransmitters (NO, H2S, and CO) as well as calcium influx could be involved. The study on isolated rat heart was performed using 4 experimental groups (n = 7 in each): (1) bolus injection of propofol (100 mg/kg body mass, i.p.); (2) L-NAME (NO synthase inhibitor, 60 mg/kg body mass, i.p.) + propofol; (3) DL-PAG (H2S synthase inhibitor, 50 mg/kg body mass, i.p.) + propofol; (4) ZnPPIX (CO synthase inhibitor, 50 μmol/kg body mass, i.p.) + propofol. Before and after the verapamil (3 μmol/L) administration, cardiodynamic parameters were recorded (dp/dtmax, dp/dtmin, systolic left ventricular pressure, diastolic left ventricular pressure, heart rate, coronary flow), as well as coronary and cardiac oxidative stress parameters. The results showed significant increases of diastolic left ventricular pressure following NO and CO inhibition, but also increases of coronary flow following H2S and CO inhibition. Following verapamil administration, significant decreases of dp/dtmax were noted after NO and CO inhibition, then increase of diastolic left ventricular pressure following CO inhibition, and increase of coronary flow following NO, H2S, or CO inhibition. Oxidative stress markers were increased but catalase activity was significantly decreased in cardiac tissue. Gasotransmitters and calcium influx are involved in pleiotropic cardiovascular effects of propofol in male Wistar rats.

Effects of atorvastatin and simvastatin on oxidative stress in diet-induced hyperhomocysteinemia in Wistar albino rats: a comparative study

Considering the well-known antioxidant properties of statins, it seems important to assess their impact on major markers of oxidative stress (superoxide anion radical, nitric oxide, and index of lipid peroxidation) to compare the antioxidative potentials of atorvastatin and simvastatin during the different degrees of hyperhomocysteinemia (HHcy) in rats. This study was conducted on adult male Wistar albino rats (n = 90; 4 weeks old; 100 ± 15 g body mass) in which HHcy was achieved by dietary manipulation. For 4 weeks, the animals were fed with one of the following diets: standard rodent chow, diet enriched in methionine with no deficiency in B vitamins (folic acid, B6, and B12), or diet enriched in methionine and deficient in B vitamins (folic acid, B6, and B12). At the same time, animals were treated with atorvastatin at doses of 3 mg/kg/day i.p. or simvastatin at doses of 5 mg/kg/day i.p. Levels of superoxide anion radical and TBARS were significantly decreased by administration of simvastatin in normal and high-homocysteine (Hcy) groups (p < 0.05). At 4 weeks after feeding with purified diets, the concentrations of the GSH, CAT, and SOD antioxidants were significantly affected among all groups (p < 0.05). Our results indicated that statin therapy had variable effects on the redox status in hyperhomocysteinemic rats, and simvastatin demonstrated stronger antioxidant effects than did atorvastatin.

The role of hydrogen sulfide in homocysteine-induced cardiodynamic effects and oxidative stress markers in the isolated rat heart

This study aimed to assess the role of H2S in homocysteine-induced cardiodynamic effects in the isolated rat heart. The hearts were retrogradely perfused according to the Langendorff technique. The maximum and minimum rates of pressure in the left ventricle (dp/dt max, dp/dt min), systolic and diastolic left ventricular pressures (SLVP, DLVP), heart rate (HR), and coronary flow (CF) were measured. A spectrophotometrical method was used to measure the following oxidative stress markers: index of lipid peroxidation (thiobarbituric acid reactive substances, TBARS), nitrite level (NO2−), superoxide anion radicals (O2•−), and hydrogen peroxide (H2O2) concentrations. The administration of 10 µmol/l DL-homocysteine (DL-Hcy) alone decreased dp/dt max, SLVP, and CF but did not change any oxidative stress parameters. The administration of 10 µmol/l DL-propargylglycine (DL-PAG) decreased all cardiodynamic parameters and increased the concentration of O2•−. The co-administration of DL-Hcy and DL-PAG induced a significant decrease in all estimated cardiodynamic parameters and decreased the concentration of NO2− and O2•− but increased the levels of TBARS and H2O2. Homocysteine shows a lower pro-oxidative effect in the presence of hydrogen sulfide (H2S), which indicates a potential anti-oxidative capacity of H2S.

Overtraining does not induce oxidative stress and inflammation in blood and heart of rats

The aim of our research was to evaluate the changes in levels of cytokines and redox state parameters in blood and isolated heart of rats subjected to different swimming protocols. Rats were divided into 3 groups: 1) controls, 2) moderately trained rats that during all 12 weeks swam 1 h/day, 5 days/week, and 3) overtrained rats that in 10(th) week swam twice, 11(th) week 3 times, and in 12(th) week 4 times a day for 1 h. After sacrificing, blood from jugular vein was collected, and the heart excised and perfused on a Langendorff apparatus. Samples of the coronary effluent were collected during coronary autoregulation. Levels of superoxide anion radical (O(2)(-)), hydrogen peroxide (H(2)O(2)), nitric oxide (NO) and thiobarbituric acid reactive substances (TBARS) were measured in plasma and coronary effluent, while reduced glutathione (GSH), activities of superoxide dismutase (SOD) and catalase (CAT) were measured in erythrocytes. Venous blood was also used for interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) determination. Moderate training protocol induced the decrease of TBARS in plasma, while both training protocols induced the decrease of O(2)(-) and H(2)O(2) in coronary effluent. There was no significant difference in levels of cytokines between groups. The results of study add evidence about beneficial effects of moderate-intensity training on blood and cardiac redox state of rats, and furthermore, shows that exercising frequently, if the intensity stays within moderate range, may not have detrimental effects.