To examine whether nutritional supplementation with SkQ1 can reduce myocardial ischemia-reperfusion injury in vivo, Wistar rats were fed a regular diet supplemented with different doses of SkQ1 for two or three weeks. Control groups of rats were fed the same diet supplemented with NaBr. Anaesthetized rats were subjected to 40-min regional myocardial ischemia and 1-h reperfusion. Myocardial infarct size was measured by 2,3,5-triphenyl tetrazolium chloride (TTC) staining method. SkQ1-fed rats (125 nmol/kg/day for two weeks and 250 nmol/kg/day for two and three weeks) revealed significantly smaller myocardial infarction and less lactate dehydrogenase (LDH) and creatine kinase-MB fraction (CK-MB) activity elevations in plasma at the end of reperfusion compared with the controls. This effect was combined with improvement of energy state of the area at risk at the end of reperfusion, namely, augmentation of adenine nucleotide content, two-fold increase in phosphocreatine, reduction of lactate accumulation and decrease of lactate/pyruvate ratio in myocardial tissue. Therefore, nutritional supplementation with SkQ1 renders the hearts resistant to ischemia-reperfusion injury affecting oxidative metabolism of postischemic cardiomyocytes.

Effects of dinitrosyl iron complex with reduced glutathione (DNIC-GS) on hemodynamics, metabolic state of the heart and myocardial infarction size were studied in vivo in rats subjected to 40-min occlusion of the anterior descending coronary artery (ADCA) and subsequent 60-min reperfusion. Intravenous bolus injection of DNIC-GS (3.10 or 0.78 micromol/kg body wt) was performed before ADCA occlusion or at the first minute of the reperfusion; the same volume of saline was infused in the control group. Nitroglycerine and nicorandil were used as reference preparations. DNIC-GS administration significantly reduced the mean arterial pressure, thus indicating vasodilative effect of NO releasing. Administration of both doses of DNIC-GS (before ADCA occlusion or at the first minute of the reperfusion) significantly limited the infarction size as compared with that in the control. Preischemic administration of 3.10 micromol DNIC-GS/kg body wt. substantially reduced activities of lactate dehydrogenase and MB-fraction of creatine kinase in blood plasma at the end of the reperfusion compared with these indices in the control. This effect was accompanied with essential improvement of energy state of the area at risk (AR) and with a lack of DNIC-GS influence on metabolism of non-ischemic area of the heart. The obtained results demonstrate that infarction remodelling after intravenous DNIC-GS administration is related to augmented preservation of aerobic metabolism and membrane integrity in post-ischemic cardiomyocytes of the AR.

Changes in nitric oxide concentration in rat myocardium in vivo during temporary occlusion of the anterior descending coronary artery, followed by reperfusion were studied by microdialysis assay in risk and intact areas by using an NO spin trap (complex of ferrous ions with N-methyl-D, L-glucamine dihiocarbamate, Fe3+-MGD2). The amplitude of the EPR signal of the NO spin adduct NO-Fe2+-MGD2 in the risk area increased during the 40-min occlusion and remained higher than the initial level during 60-min postischemic reperfusion, indicating a substantial nitric oxide production. The size of the infarction in the risk area by the end of reperfusion was 47 +/- 3 %, the contents of ATP, phosphocreatine, and total creatine decreased to 44 +/- 4, 51 +/- 5, and 60 +/- 3 %, correspondingly, as compared with initial values, and the level of lactate was six times higher than the initial one. In the intact area of the left ventricle, the level of nitric oxide and high-energy metabolites did not change throughout the experiment. It was shown that the intensive nitric oxide production, in acute regional ischemia and reperfusion are related to the disturbance of energy metabolism, the damage to cytoplasmic membranes, and the death of cardiomyocytes.

The effect of regional ischemia on canine myocardial in situ free radical species was studied by the EPR method. Rapid fixation of heart muscle samples by freezeclamping was performed at the following physiological states: native myocardial blood circulation, regional ischemia with the presence of collateral circulation, total ischemia, and postischemic reperfusion. EPR spectra of the samples at -40 degrees C exhibited two free radical signals from the semireduced forms of ubiquinone and flavine coenzymes. Upon transition from normal blood supply to regional ischemia, an increase in the contribution of the flavine signal was registered, but reperfusion resulted in the recovery of the characteristics of EPR signals. It was found that the increase in the intensity of collateral circulation in the ischemic area led to an increase in the portion of ubisemiquinone in the integral EPR signal, whereas in total ischemia this signal was not registered. It was shown that the changes in spectral characteristics of integral free radical signals are accompanied by changes in their relaxation parameters.

An experimental mathematical model was proposed to assess the efficiency of experimental myocardial infarction (MI) size limitation. A canine model of occlusion-reperfusion myocardial lesion was used in an acute experiment with an open chest. 90-minute occlusion and 4-hour reperfusion were performed by carotid coronary bypass surgery. The necrotic zone and the risk area were visualized by double perfusion with tetrazolium staining. Retrograde coronary blood flow was used as a measure of collateral blood flow. The multiple linear regression equation with values of the risk zone and retrograde blood flow/risk area ratio used as independent variables enabled the size of myocardial infarction to be highly accurately predicted. Comparison of the true size of MI with the "expected" one provided methods for quantitative assessment of pharmacological limitation of MI sizes. Calculating an individual value for each animal made it possible to examine its relation to coronary circulation parameters and facilitated comparison of benefits from various agents.

Acute dog experiments involving the perfusion of donor coronary arteries demonstrated that alpha-adrenoreceptor stimulation in the presence of a beta-adrenergic block resulted in a 30% drop of coronary flow. This response is maintained at low perfusion coronary blood pressure values (up to 25 +/- 13 mmHg, p less than 0.02), whereas coronary dilatation reserve is already fully depleted at 60 +/- 8 mmHg, suggesting that the degree of coronary arterial stenosis associated with coronary insufficiency may be a decisive factor shaping coronary response to alpha-adrenoreceptor stimulation.

In closed chest dogs with controlled perfusion of the left coronary artery coronary blood flow was reduced by 10, 20, 30, 40, 50 and 70%. Diffusion capacity of myocardial capillary bed (permeability surface area product) decreased in all but the first (10%) series of experiments. 23-64% fall of the product occurred irrespective of coronary vessel reserve state but with respect to the degree of blood flow reduction. The amount of coronary influx possibly determined the number of perfused capillaries in the heart. Thus, 20% and more reduction of coronary blood flow cannot be compensated at the level of myocardial capillary bed.

Extraction of 201TlCl3 diffusing into the heart tissue under conditions of its normal functioning and in the presence of ischemia was appraised on a model with isolated coronary perfusion of the myocardium by the dual-tracer method. From analysis of the discharge curve of the tracers used it is concluded whether or not microcirculation of the perfused area of the heart is uniform or heterogeneous. It was established that in myocardial ischemia, 201TlCl3 does not accumulate in the interstitium, which makes it possible to evaluate the zones with diminished inclusion of 201TlCl3 encountered in scanning of the heart as corresponding to diminished blood supply.

It is shown that the diffusion capacity of the capillary channel diminishes in myocardial ischemia. In unchanged or increased capillary permeability this effect may only be explained by a functional shunt of the affected cardiac area. Intracoronary administration of a carrier of biologically active substances in the form of microspheres of modified Sephadex does not aggravate irregularity in the blood supply to the zone of ischemia, which is evidence of the adequacy of the organ reserves of the functional shunt in this situation.