L. M. Belkina

The role of lipid peroxidation in pathogenesis of arrhythmias and prevention of cardiac fibrillation with antioxidants

SummaryThe present paper shows the arrhythmogenic effect of a direct induction of lipid peroxidation (LP) on isolated auricles; it is demonstrated that preendured stress potentiates this effect, while antioxidants prevent it. Subsequently, in studying the mechanism of the LP arrhythmogenic effect it was established that stress, like the LP induction, disorders the activity of Na, K-ATPase and accelerates thermodenaturation of this enzyme which plays a key role in maintaining the transmembrane potential and the electrical stability of the heart. Antioxidants prevent the enumerated shifts. Based on these data, the antioxidant BHT was successfully applied for prevention of the fall in cardiac fibrillation threshold in stress and experimental myocardial infarction, and also for prevention of cardiac fibrillation itself under acute ischemia and reoxygenation of the heart.

HSP70 Stress Proteins, Nitric Oxide, and Resistance of August and Wistar Rats to Myocardial Infarction

Accumulation of HSP70 stress proteins in the myocardium and blood content of nitrite/nitrate in August rats with modeled myocardial infarction surpassed these parameters in Wistar rats less resistant to cardiovascular disorders by 2-2.5 and 1.8 times, respectively. Our results suggest that various resistance of August and Wistar rats to myocardial infarction is related to genetically determined differences in the activity of HSP70 and nitric oxide systems.

Adaptation of the cardiovascular system to postinfarction cardiosclerosis in rats with congenital adrenoreactivity of the myocardium

Three months after myocardial infarction the severity of heart failure and size of postinfarction scars in August rats with inherently reduced adrenoreactivity of the myocardium were similar to those in Wistar rats. The mortality rate in August rats was 2.5-fold lower than in Wistar rats. During the postinfarction period, myocardial adrenoreactivity in August rats remained lower, while the efficiency of cardiac function was 62% higher than in Wistar rats. The incidence of epinephrine-induced arrhythmias in August rats was much lower than in Wistar rats.

Peculiarities of autonomic regulation assessed by variability of hemodynamic parameters in rats with different stress resistance.

Analysis of contribution of sympathetic and parasympathetic systems into heart rate variability carried out using atenolol and atropine showed that August rats are characterized by enhanced tone of the sympathetic system and reduced tone of the parasympathetic system compared to Wistar rats. Reduced tone of the parasympathetic system is also confirmed by lower sensitivity of the baroreflex. Blockade of NO synthesis with Nω-nitro-L-arginine more markedly increased blood pressure variability in August rats compared to Wistar rats. The data attest to a certain rigidity of the autonomic cardiovascular regulation in August rats.

CA-TRANSPORTING SYSTEM OF THE LEFT VENTRICULAR SARCOPLASMIC RETICULUM IN THE RAT HEART AND DAMAGE TO ITS MEMBRANE DURING ISCHEMIA AND REPERFUSION

Ischemia and reperfusion of various duration are shown to result in a nonlinear increase in the level of free Ca in myocardial homogenates. A striking dissociation has been observed in the effect of ischemia and reperfusion on the rate of Ca transport in the sarcoplasmic reticulum, on the one hand, and the permeability of its membranes on the other.

Heart resistance to oxidative stress in rats of different genetic strains

In August rats reperfusion after regional myocardial ischemia in situ or intracoronary administration of hydrogen peroxide less significantly suppressed contractile activity of the heart compared to Wistar rats. Activities of catalase and superoxide dismutase in the myocardium during reperfusion remained unchanged in August rats. In Wistar rats a profound inhibition of cardiac function was accompanied by a decrease in enzyme activity.

August Rats are More Resistant to Arrhythmogenic Effect of Myocardial Ischemia and Reperfusion than Wistar Rats

As differentiated from Wistar rats, myocardial ischemia and reperfusion produce no ventricular fibrillation in August rats. Pretreatment with nitric oxide synthase inhibitor Nw-nitro-L-arginine increased mortality rate in August rats with acute myocardial infarction from 20 to 40%. Under these conditions mortality rate in Wistar rats increased from 50 to 71%. Interstrain differences in the resistance of these animals to the arrhythmogenic effect of ischemia are probably associated with higher activity of the nitric oxide system in August rats compared to Wistar rats.

Effect of electroacupuncture on systemic hemodynamics in rats with postinfarction cardiosclerosis

Electroacupuncture decreased total peripheral vascular resistance and increased cardiac output in 12-week-old postinfarction rats without cardiac insufficiency, while opposite changes were observed in rats with cardiac insufficiency. After the electroacupuncture course, norepinephrine decreased cardiac output in the rats with cardiac insufficiency, while acetylcholine increased it to a much higher extent than in the control rats that were not subjected to physiotherapy.

Effect of preliminary adaptation to transauricular electrostimulation on the content of catecholamines and met-enkephalin in rat heart and adrenals in stress and acute myocardial infarction

Adaptation to transauricular electrostimulation decreases the content of epinephrine in the adrenal glands and norepinephrine in the heart. Immobilization stress has no appreciable effect on the content of catecholamines in the heart and adrenal glands. In animals with myocardial infarction, the content of norepinephrine in the heart decreases 2-fold, while the content of epinephrine in the adrenals decreases inconsiderably. Adaptation to transauricular electrostimulation is associated with a rise in met-enkephalin concentration. Preadaptation induces a more pronounced rise of met-enkephalin and promotes normalization of epinephrine in the adrenals, without changing the content of norepinephrine in the heart.

Effect of vitamin E deficiency on cardiac arrhythmias induced by acute ischemia

The ability of extracts of halves of the brain [2, 5, 7] and spinal cord (Tables 1 and 2) to induce effects confined to the homonymous side of the spinal cord is proof that the distribution of LF in these two parts of the CNS is similar in principle of distribution of LF in the nervous system, reflecting the similarity of peptide composition of brain and spinal cord LF and the identical direction of changes in peptide concentrations in several situations, taken together, explain the hitherto unexplained fact that in vestibulopathy asymmetry of muscle tone of the recipients hind limbs is caused by extracts not only of the spinal cord (Tables 1 and 2), but also of the brain [6]. Asymmetry of the effects of LF is perhaps linked with asymmetry of opiate receptors, as is sho~ by abolition of the action of LF in the presence of the opiate antagonist. This hypothesis is in agreement with data on asymmetrical changes of muscle tone under the influence of opioid peptides [i, 4].