Influence of Low Concentrations of Carbon Monoxide on Metabolism of Isolated Heart under Conditions of Ischemia-Reperfusion

The purpose of the study was to determine the effect of different concentrations of carbon monoxide on the metabolism of isolated mice hearts. Materials and methods. To elucidate the effect of low concentrations of carbon monoxide on the myocardium, we performed retrograde perfusion of isolated hearts of laboratory mice with Krebs-Henseleit solution, which was saturated with carbon monoxide for 5, 10, and 30 minutes. We then determined how different concentrations of carbon monoxide affected coronary volumetric flow rate, myocardial glucose and calcium uptake, creatinine release, and aspartate aminotransferase release. During perfusion, R-wave amplitude and R-R interval were measured using an electrocardiograph. To determine the effect of ischemia on the heart muscle during perfusion with solutions of different concentrations, we measured the area of the affected myocardium after staining with 2,3,5-triphenyltetrazolium chloride. Results and discussion. After these studies, it was found that different concentrations of carbon monoxide had a dose-dependent effect on the isolated mouse heart. However, the dependence of the effects does not follow the pattern «lowest concentration – lowest effect». At the same time, an increase in concentration did not mean an increase in adverse effects on the myocardium. Even on the contrary, the smallest concentration led to increased signs of ischemic myocardial damage. In particular, the use of the solution, through which carbon monoxide was passed for 5 minutes, caused vasoconstrictor effect during perfusion. At the end of reperfusion, vasoconstrictor effect was observed after using a solution through which carbon monoxide was passed for 10 minutes. Increased glucose uptake was observed in the group with 30-minute carbon monoxide permeation against the background of the minimal myocardial creatinine release. In this group there was also a decrease in Ca2+ loss at the beginning of reperfusion (immediately after ischemia). The above phenomenon explains the least degree of ischemic myocardial damage in the isolated mouse heart. The obtained data should be expanded. Since it is difficult to accurately determine the dose of carbon monoxide, then the use of donor compounds is promising. Such compounds include CORM-2 and CORM-3. Under physiological conditions, they decompose in a controlled manner, releasing a specific amount of carbon monoxide. Conclusion. The obtained results indicate that at different concentrations of carbon monoxide can differently influence different structures of cardiomyocyte: at one concentration it binds to calcium channels, other concentrations influence ion channels of plasma membrane, which can explain all these dependencies

Direct cardiotoxicity of lead

Lead is a heavy metal pollutant that constitutes frequent exposomes. It is nonbiodegradable and has a nonsafe limit of exposure. It has multisystemic effects, and most of the cardiac effects have been discovered to be indirect. There are strong similarities between Ca2+ and Pb2+ in their chemistry. Because cardiac function is dramatically dependent in extracellular Ca2+, as well as in precise control of intracellular Ca2+, we tested if Pb2+ could antagonize Ca2+-dependent effects in a short amount of time. Acute exposure of isolated hearts showed a negative inotropic effect. In guinea pig isolated cardiomyocytes loaded with a Pb2+-specific dye (Leadmium green), our results showed that there was an associated increment in fluorescence related to extracellular stimulation blocked by 1–5 µM DHP. Calcium currents were partially blocked by extracellular Pb2+, though currents seemed to last longer after a fast inactivation. Charge movement from gating currents was slightly hastened over time, giving an appearance of a slight reduction in the Cav1.2 gating currents. Action potentials were prolonged in Pb2+ compared with Ca2+. In isolated cardiomyocytes loaded with Ca2+-sensitive dyes, Ca2+ variations promoted by extracellular stimuli were affected in space/time. As Pb2+ could interfere with Ca2+-sensitive dyes, we measured contraction of isolated cardiomyocytes under extracellular stimuli in Pb2+. In both Ca2+ dye fluorescence and contractions, Pb2+ disorganizes the pattern of contraction and intracellular Ca2+ homeostasis. Our results suggest that (1) Pb2+ enters to cardiomyocytes through Cav1.2 channels, and (2) once it enters the cell, Pb2+ may substitute Ca2+ in Ca2+-binding proteins. In addition to these direct mechanisms related to Pb2+ competition with Ca2+-binding sites, we cannot discard a direct contribution of Pb2+ redox properties.

Acute exposure to the chemotherapy cisplatin has a biphasic effect in cardiac contractility

Cancer and cardiovascular diseases are the main causes of death in Uruguay and developed countries. In clinical practice, there is often the need to administrate chemotherapy with cisplatin (CTP) to patients with cardiovascular comorbidities. The aim of this work is to characterize the possible detrimental effects in cardiac function by the acute exposition to CPT using isolated heart and cardiomyocytes from guinea pigs (Cavia porcellus). All the procedures regarding animal experimentation were performed following approved protocols by the university ethics committee. Isolated hearts were placed in a Langendorff system and perfused with Tyrode 1.8 mM Ca2+ as control medium, or with extracellularly added CPT (0–100 µM). Tension was recorded with a gauge force transducer attached to the papillary muscle and electrical responses were measured with Ag-AgCl electrodes placed in surface extremes near the papillary muscle. Cardiomyocytes were isolated by enzymatic methods. Data were obtained by patch clamp and confocal microscopy with Rhodamine and Fluo dyes sensitive to Ca2+ binding. Non-parametric t tests were used for data comparison. The best fit of Hill’s equation to dose–response curves was done using nonlinear regression methods. In isolated hearts, CPT showed a biphasic effect over the development of tension, increasing up to 5–10 µM to decrease at higher concentrations. In isolated cardiomyocytes, Ca2+ currents were stimulated and inhibited by CPT in a similar dose. Confocal microscopy showed an increment and a reduction of relative fluorescence of the calcium-sensitive dyes with CPT as well. Our results suggest that CPT may affect cardiac contraction and automatism upon acute exposure of the heart, presumably by blocking L-type (Cav1.2) calcium channels and interference with molecules involved in maintaining the homeostasis of intracellular Ca2+.

The Potential protective role of astaxanthin on doxorubicin-induced cardiac toxicity in rats

Background and Aim of Work Doxorubicin (DOX) is one of the most commonly used effective anticancer drugs, through its inhibition of topoisomerase II, DNA replication and repair. In addition, DOX leads to generation of semiquinone free radicals and oxygen free radicals which attack DNA and oxidize DNA bases. However, the clinical use of doxorubicin is limited by its adverse effects such as cardiotoxicity, which is acute and occurs within 2-3 days of its administration. Recently, the potential health benefits of Astaxanthin were investigated, however, the protective effect of astaxanthin supplementation on cardiac dysfunction induced by Doxorubicin is not clearly investigated. The aim of the present study is directed to investigate the possible role of astaxanthin (xanthophyll carotenoid) in protection against DOX- induced cardiac toxicity, and to elucidate the underlying mechanism(s). Materials and Methods Animals used were 47 adult male albino rats, which were randomly allocated into four groups. Control group(C): received 0.1ml/100gm BW i.p. saline injections for 7 successive days. DOX-treated group: received 0.1ml/100gm BW i.p. saline injections for 7 successive days, followed by a single i.p. injection of DOX, 20 mg/kg i.p. on the 7th day. ATX-treated group: received 40mg/kg/day BW i.p. ATX injections for 7 successive days. ATX+DOX treated group: received 40mg/kg/day BW i.p. ATX injections for 7 successive days, followed by a single i.p. injection of DOX, 20 mg/kg i.p. on the 7th day. At the end of the study, the overnight fasted rats were subjected to final arterial blood pressure measurement. Rats were then weighed and anaesthetized with 40 mg/kg B.W i.p. thiopental sodium. Then, ECG was recorded, blood samples were collected from abdominal aorta and centrifuged. The resulting plasma was used for measurement of plasma cardiac Troponin I (cTnI) and plasma Cytochrome C. The heart was subjected to In vitro study of isolated hearts perfused in langendorff preparation. Hearts and ventricles were weighed. The left ventricle was then stored at -80οC for later determination of cardiac tissue iron. Statistical Analysis was made using 1-way ANOVA for difference between means of different groups. Ethics Committee The study protocol was approved by the Research Ethical Committee of Faculty o fMedicine Ain Shams University (Reference No. FWA00017585). Results The systolic blood pressure was increased significantly in the DOX treated group compared to the control group. All of the systolic, diastolic and mean arterial blood pressures were significantly decreased in the ATX +DOX treated group compared to the DOX treated group. Heart rate was significantly increased in the ATX +DOX treated group compared to the control group, and compared to the DOX treated group. PT and PT/LVW were significantly increased in the ATX +DOX group compared to both of the DOX group and the control group. In addition, PT and PT/LVW were significantly increased in the ATX-treated group compared to the DOX group. The TPT was prolonged in the DOX group compared to the control group and this prolongation was statistically significant in pre-ischemia and 5 minutes after reperfusion of the isolated hearts, and was significantly shortened in the ATX-treated group and ATX +DOX group compared to the DOX. Also, TPT was significantly shortened in the ATX-treated and in the in the ATX +DOX groups compared to the control group. HRT was significantly prolonged in the DOX group compared to the control group. However, HRT was significantly shortened in the ATX-treated and ATX +DOX groups compared to the DOX group, and in the ATX +DOX group compared to the control group. The MFR and MFR/LVW were significantly decreased in the DOX group compared to the control group. However, the MFR was significantly increased in each of the ATX-treated group and ATX +DOX group when each was compared to the DOX group. Moreover, MFR was significantly increased in the ATX +DOX group compared to the control group. Each of plasma cardiac Troponin, plasma Cytochrome C and Cardiac Tissue Iron were significantly increased in the DOX group compared to the control group, and all were significantly decreased in the ATX-treated group when compared to DOX group, and in the ATX +DOX group when compared to the DOX group. No significant changes were detected in body weight, heart weights and ECG parameters between the different studied groups. Conclusion Doxorubicin produces acute cardiotoxic effects and impairs systolic and diastolic cardiac functions, which is due to increased oxidative stress, mitochondrial instability and iron accumulation in the cardiac tissue. Astaxanthin exerts a major cardioprotective activities against DOXinduced cardiotoxicity, probably due to its major antioxidant and iron chelation properties.

Universal inverse square relationship between heart rate variability and heart rate

In our previous study, we analyzed heart rate variability and heart rate from a large variety of cardiac preparations (including humans, living animals, Langendorff-perfused isolated hearts, and single sinoatrial nodal cells) in diverse species, combining our data with those of previously published articles. The analysis revealed that regardless of conditions, heart rate variability (for the purposes of the study assessed as standard deviation) of beat-to-beat intervals heart rate follows a universal exponential decay-like relationship. Numerical simulations of DI variability by adding a randomly fluctuating term to net current revealed a similar relationship. In the present study, using a Taylor series, we found that this relationship is, in fact, inverse square, and we derive an explicit formula for sd(CL) vs. heart rate with biophysically meaningful parameters.

Abstract P138: Long-term Effects Of Severe Caloric Restriction To The Heart Function

Severe caloric restriction (sCR) increases the risk for acute cardiovascular disease. Less understood are the long-term effects on cardiovascular disease risk after the sCR period has ended. We investigated the effects of sCR on heart structure and function months after refeeding (sCR-Refed). Female Fischer rats (3-months-old) were maintained on (CT) ad libitum or a 60% caloric restricted diet for 2 weeks. Thereafter, all rats received ad libitum chow for 3 months and they were analyzed by precision ultrasound to assess their heart function. After imaging, the animals were sacrificed and the hearts were subjected to ischemia-reperfusion (I/R) using a Langendorff preparation. After 2 weeks of sCR, rats lost 15% of their initial body weight (BW) [% (100*(Final-Initial/Initial)): CT, 1.5±0.8 vs sCR, -15.4±1.1; p<0.001;n=8]. After 3 months of refeeding, there was no detectable difference in BW between CT and sFR-Refed groups. Isolated hearts from the sCR-Refed rats exhibited worse myocardial pathology after I/R compared to CT rats. The parallel orientation of myofibers and striations normally present in cardiomyocytes was lost in sCR-Refed rats. Further analysis revealed uneven blood-filling of the microcirculatory vessels and prominent interstitial edema of the myocardium. Hearts from sCR-Refed rats had more atrophied cardiomyocytes than CT [Atrophied/Total (%): CT, 0.2±0.1 vs sCR-Refed, 50.6±1.1; p<0.001; n=5]. The number of arrhythmic events during a 30 min ischemic interval in isolated hearts doubled after 2 weeks on the sCR diet ( data not shown ) and remained doubled 3 months later [Arrhythmias (% of time): CT, 34±8 vs sCR-Refed, 68±9; p=0.02; n=8]. Ultrasound imaging showed no difference in stroke volume, coronary perfusion pressure and left ventricular mass. However, the thickness of the left ventricular posterior wall was significantly reduced in sCR-Refed rats [(mm): CT, 2.55 ±0.03 vs sCR-Refed, 2.10±0.04; p=0.002; n=4]. These findings indicate heart structure and function remained damaged months after the sCR period ended and BW was restored. These studies have adverse cardiovascular risk implications for who are subjected either voluntarily (crash diets) or involuntarily (very low food security) to periods of inadequate caloric intake.

Effect of ATP and molsidomine combination on contractile function of isolated adult and old rat hearts during adequate coronary perfusion, at ischemia and reperfusion

Pathology of the cardiovascular system occupies a major place in the structure of diseases of the elderly and old patients. Metabolic disturbances are very important in ischemic damages of myocardium in the elderly and old people. So, drugі with metabolic mechanism of action is very ppromising in the treatment of elderly patients with cardiovascular diseases. The relevance of this study is determined by the feasibility of using drugs of metabolic action, which have a beneficial effect on the metabolism of cardiomyocytes, improve blood supply to the myocardium, increase its contractile function. The effect of ATP-molsidomine combination on myocardial contractility in different age animals was stuiesy in vitro experiments. The experiments on the isolated hearts from adult and old rats have shown that combined use of ATP and molsidomine did not significantly affect the contractility of the isolated hearts of adult rats under different perfusion regimes. In old rats, the use of ATP-molsidomine combination had a positive effect on the contractile function of the myocardium under the influence of damaging factors (ischemia, reperfusion): prevented a decrease of left ventricular developing pressure and its first derivative (velocity of pressure rise and velocity of pressure decline) and accelerated its growth during reperfusion. Co-administration of ATP and molsidomine during ischemia had a positive effect on the heart rhythm and restored heart rate at the reperfusion period in adult and old rats. The results of the study indicate a positive effect of the ATP-molsidomine combination on the myocardial contractility in old rats. Combined use of ATP and molsidomine exerted a favourable influence on the heart rhythm under damaging factors both in the adult and old animals. Key words: ATP; molsidomine; isolated rat heart; myocardial contractility; ageing

Combination effects of gallic acid and cyclosporine A during ischemia/ reperfusion on rat electrocardiogram parameters and arrhythmia

Introduction: Myocardial ischemia leads to electrical disturbance in the heart because of reactive oxygen specious. This study aimed to investigate the effects of gallic acid and cyclosporine A (CsA) together on electrocardiogram parameters in myocardium following ischemia - reperfusion (I/R) in isolated hearts. Methods: In this research, 50 Wistar rats weighing 250-300g were randomly divided into the 5 following groups: control, sham and gallic acid (7.5, 15 and 30mg/kg) in combination with CsA (0.2μM). On the eleventh day, the hearts were removed and perfused with Krebs solution and ischemia was induced for 30min. Then, cyclosporine was administered for 10min at the 10 minutes before reperfusion and 10 minutes the beginning of reperfusion. By placing the electrode, the parameters of RR, PR, QT, TpeakTend, JT and QTcB interval, ST elevation, R, P, Q, S, T amplitude were recorded before ischemia and during reperfusion. Results: This study showed that RR, JT, interval, p duration, ST elevation and PVC numbers of control were increased during ischemia compared with sham and decreased using gallic acid (7.5, 15 and 30mg/kg) in combination with CsA. In addition, P, R, S, T amplitude during the ischemia were decreased in control compared with sham and increased with gallic acid (15mg/kg) in combination with CsA. Conclusion: In conclusion, the optimal combination of both drugs decreased arrhythmia occurrence while increased electrical velocity of conduction and wave amplitudes in isolated myocardium after ischemia reperfusion injury.

Di-4-ANEPPS Modulates Electrical Activity and Progress of Myocardial Ischemia in Rabbit Isolated Heart

AimsAlthough voltage-sensitive dye di-4-ANEPPS is a common tool for mapping cardiac electrical activity, reported effects on electrophysiological parameters are rather. The main goals of the study were to reveal effects of the dye on rabbit isolated heart and to verify, whether rabbit isolated heart stained with di-4-ANEPPS is a suitable tool for myocardial ischemia investigation.Methods and ResultsStudy involved experiments on stained (n = 9) and non-stained (n = 11) Langendorff perfused rabbit isolated hearts. Electrophysiological effects of the dye were evaluated by analysis of various electrogram (EG) parameters using common paired and unpaired statistical tests. It was shown that staining the hearts with di-4-ANEPPS leads to only short-term sporadic prolongation of impulse conduction through atria and atrioventricular node. On the other hand, significant irreversible slowing of heart rate and ventricular conduction were found in stained hearts as compared to controls. In patch clamp experiments, significant inhibition of sodium current density was observed in differentiated NG108-15 cells stained by the dye. Although no significant differences in mean number of ventricular premature beats were found between the stained and the non-stained hearts in ischemia as well as in reperfusion, all abovementioned results indicate increased arrhythmogenicity. In isolated hearts during ischemia, prominent ischemic patterns appeared in the stained hearts with 3–4 min delay as compared to the non-stained ones. Moreover, the ischemic changes did not achieve the same magnitude as in controls even after 10 min of ischemia. It resulted in poor performance of ischemia detection by proposed EG parameters, as was quantified by receiver operating characteristics analysis.ConclusionOur results demonstrate significant direct irreversible effect of di-4-ANEPPS on spontaneous heart rate and ventricular impulse conduction in rabbit isolated heart model. Particularly, this should be considered when di-4-ANEPPS is used in ischemia studies in rabbit. Delayed attenuated response of such hearts to ischemia might lead to misinterpretation of obtained results.