Quercetin is a plant-derived bioflavonoid with potentially beneficial effects on the cardiovascular system. Studies focused on the efficiency of flavonoids against ischemia-reperfusion (I/R) injury have demonstrated that quercetin exerts robust protective effects in renal, cerebral, and hepatic I/R models. However, there is only limited evidence about the effect of quercetin on myocardial I/R injury. Therefore, the aim of the current study was to examine the effect of quercetin on isolated rat heart during ischemia and reperfusion. Rat hearts perfused according to Langendorff at 37 degrees C were examined during 25 min global ischemia followed by 120 min reperfusion. Quercetin (15 micromol/L) was administered either 15 min before ischemia (group Q1), or during the entire reperfusion period (group Q2). Changes in functional parameters of the hearts were measured during the initial 40 min of reperfusion. At the end of the experiment, the hearts were stained with tetrazolium to estimate the size of infarction (IS). Our study showed that quercetin improved postischemic recovery of functional parameters of isolated hearts in both treated groups. This improvement was manifested by significantly higher values of left ventricular developed pressure (LVDP) and the maximal rates of pressure development and fall (+(dP/dt)max and -(dP/dt)max) and by significantly lower increase of end-diastolic pressure. Coronary flow was not significantly changed during reperfusion in the group treated before ischemia, but was significantly increased in the group treated during reperfusion. Quercetin also significantly reduced IS in both groups, more markedly in postischemically treated group. We conclude that acute quercetin treatment exerts significant positive effects on isolated hearts during I/R injury. These results are consistent with the beneficial effects of quercetin and other flavonoids on the cardiovascular system.

Among the cardiovascular pathologies, ischemic heart disease is a serious medical problem that can result in cardiac injury and (or) heart failure. The aim of the present study was to test the hypothesis that neuropeptide oxytocin induces cardioprotective effects on ischemia-reperfusion-induced myocardial damage. The functional parameters of isolated Langendorff-perfused rat hearts were recorded before and after global 25 min ischemia and subsequent reperfusion. The infarct size was determined by a computerized planimetric method. The results showed that oxytocin produced negative chronotropic effect even at low concentrations (90-125 nmol/L). Perfusion with oxytocin before ischemia resulted in significant reduction of the infarct size (p<0.01), which was about 66% smaller than that in the control group. To evaluate the functional mechanisms involved, further experiments were performed under conditions of constant heart rate. The lower dose of oxytocin (90 nmol/L), which was ineffective in spontaneously beating hearts, induced a significant decrease of contractility. Elimination of the negative chronotropic effect of oxytocin prevented its cardioprotective action. In conclusion, our results demonstrated an attenuation of the infarct size in oxytocin-treated hearts, indicating a cardioprotective effect of oxytocin. The data suggest that the negative chronotropic action of oxytocin participates in its protective effects on ischemia-reperfusion-induced myocardial injury.

Quercetin, a polyphenolic compound present in various types of food, has been shown to exert beneficial effects in different cardiac as well as non-cardiac ischemia/reperfusion (I/R) models in adult animals. However, there is no evidence about the effects of quercetin on I/R injury in non-mature animals, despite the fact that efficiency of some interventions against I/R is age-dependent. This study was aimed to investigate the effects of chronic quercetin treatment on I/R injury in juvenile and adult rat hearts. Juvenile (4-week-old) as well as adult (12-week-old) rats were treated with quercetin (20 mg/kg/day) for 4 weeks, hearts were excised and exposed to 25-min global ischemia followed by 40-min reperfusion. Functional parameters of hearts and occurrence of reperfusion arrhythmias were registered to assess the cardiac function. Our results have shown that quercetin improved post-ischemic recovery of LVDP, as well as recovery of markers of contraction and relaxation, +(dP/dt)max and –(dP/dt)max, respectively, in juvenile hearts, but not in adult hearts. Quercetin had no impact on incidence as well as duration of reperfusion arrhythmias in animals of both ages. We conclude that the age of rats plays an important role in heart response to quercetin treatment in the particular dose and duration of the treatment. Therefore, the age of the treated subjects should be taken into consideration when choosing the dose of quercetin and duration of its application in prevention and/or treatment of cardiovascular diseases.