[Protective effect of extracellular K+ in the myocardium in disorders of energy metabolism]

In an experimental study on isolated isovolumetric guinea-pig hearts, a 2.2-fold reduction of the coronary duct combined with metabolic block caused by dinitrophenol (0.05 mM) resulted in an eleven-fold drop in the attained pressure, and a shorter electric systole, a smaller P wave, and an ST displacement on the ECG. Deep suppression of mechanical and electric activity was combined with reduced glycogen content, and greater K+ and Na+ withdrawal from the heart. Quantitatively, the drop in contractility correlated with K+ withdrawal and ST displacement. A sudden increase in coronary perfusion rate was accompanied by a rapid increase in the rate of K+ elimination from the heart which was proportionate to the rate of hyperfusion, with a simultaneous transitory rise in attained pressure, a great increment in diastolic pressure and the emergence of arrhythmia and fibrillation, the severity of the changes correlating with the degree of K+ loss. A moderate increase in K+ concentration of the perfusate prevented the development of fibrillation and drastically reduced the degree of contracture and glycogen drop during hyperfusion. The obtained results suggest that moderate accumulation of extracellular K+ during the early phase of energy generation disorder can be of a protective nature, as it contributes to a sharp reduction in contractility and energy spending to improve cell survivability in critical conditions.

[Correlation of the parameters of myocardial contraction and relaxation in compensatory cardiac hypertrophy]

The parameters of myocardial contraction and relaxation were determined from the left ventricular pressure curves obtained in closed chest rabbits. One month after the creation of ascending aorta stenosis when the relative weight of the left ventricle increased by 54% as compared to the control, systolic pressure was higher by 42% and maximum rate of pressure development by 47%. This increase corresponded to the degree of left ventricular hypertrophy so that the load on the unit of myocardial mass did not change. No changes were found in the contractility index. The index of relaxation, however, determined by the relation between the maximum rate of relaxation and the developed pressure and characterizing the function of the myocardial relaxation system was 20% lower than that of the control. This was associated with the decrease of the diastolic pause by 27%. The slowing down of relaxation is one of the first and must' signs of compensatory function of the heart.

[Changes in the noradrenaline content in the rabbit myocardium in electrostimulation of the aortic arch]

Excessive stimulation of reflexogenic zone of rabbit aortic arch resulted in impairments of noradrenaline tissue reserves in heart muscle. Administration of one of the precursors of noradrenaline l-DOPA not only prevented the decrease in tissue noradrenaline content in myocardium, but restored completely its reserves, exhausted by electrostimulation of the aortic arch.

[Glucose-6-phosphate dehydrogenase of neurogenically damaged heart]

Neurogenic damage of the myocardium by electrostimulation of the aortic arch led to deficiency of tissue noradrenaline (the sympathetic nervous system mediator). Simultaneously there was a marked rise of the glucose-6-phosphate dehydrogenase activity. Preliminary administration of the RNA synthesis inhibitor--actinomycin D--fully prevented the increase of this enzyme activity in the myocardium produced by its neurogenic damage. The data obtained testified to the acceleration of induction of this enzyme in the myocardium in case of its neurogenic damage, this correlating with the change of tissue noradrenaline balance.

[Effect of a new central adrenolytic on cardiac metabolic indices in neurogenic damage]

It is shown that in rabbits subjected to an electric stimulation of the aortic arch there developed concurrently with depletion of tissular norepinephrine reserves in the myocardium also gross metabolic disorders. A preliminary introduction of the drug izm-611 by blocking central alpha-adrenoreseptors at the same time prevented depletion of the tissular norepinephrine reserves and development of disturbances of the energy exchange in the myocardium caused by its neurogenic damage.

[Adrenergic regulation and adrenoreactivity of the rat heart during adaptation to altitude hypoxia]

Male albino rats were adapted to 6 km "altitude" in barocamber. Responses of their hearts in open chest and on artificial respiration to noradrenaline and propranolol were studied. Values of the heart contractory function were by 32-140% higher in experimental animals than in control those. This excess could be eliminated by propranolol which shows it to be due to exaggerated effect of the adrenergic regulatory link. Adrenaline raises the heart function almost up to the maximal limit in adapted animals. This is followed by an increased rate of disappearance of the noradrenaline inotropic effect.

[Contractile function of the heart and its reactivity to noradrenaline in the process of the bodies adaptation to moderate altitudes]

In acute experiments on rats adapted for 4 weeks to the altitude of 2100 m it was found that at the early period of altitude adaptation the left ventricular systolic pressure and the maximal rates of pressure rise and fall considerably exceeded the values of control tests conducted in Moscow. Later on the parameters of the cardiac contractile function stabilized gradually. In 4 weeks the heart of adapted animals showed a greater increment of the contractility parameters in response to noradrenaline injection and a higher stability of the contractile function at very high heart rates.

[Glucose-6-phosphate dehydrogenase in rat liver and myocardium following toxic doses of noradrenaline]

Administration of toxic doses of noradrenaline into rats led to exhaustion of noradrenaline reserves in liver and heart tissues with the simultaneous increase in the activity of glucose-6-phosphate dehydrogenase in the tissues. Actinomycin D, administered together with noradrenaline, completely prevented the elevation of the G6PD activity in the tissues studied. The data obtained suggest that sympathetic nervous system and its mediator are responsible for regulation of the rate of enzymatic protein synthesis in tissues.

[Comparison of the contractile function of the heart in hares and rabbits under conditions of relative rest and under resistance loading]

A comparison was conducted between the contractile function of the heart of hares and rabbits at rest and under isometric contractions regimens, and under such conditions the concentration of ATP and its breakdown products was studied in the myocardium of both species. It was demonstrated that the cardiac muscle of hares adapted by the evolution to the performance of intensive work does not possess any increased ability of developing systolic tensions, or any increased power of the ATP resynthesis apparatus. The advantage of such a heart-- its ability to pump an increased blood volume -- must be ensured by some different mechanism that requires still further investigations.

[Activity of various enzymes of energy metabolism of the myocardium after neurogenic injury]

A 3-hour electrostimulation of the aortic arch in rabbits was followed by the exhastion of the tissue noradrenaline stores in the myocardium accompanied by increase in the activity of the glycolysis enzymes and of the enzyme limiting the process of the pentosophosphate route-G-6-PDH. The use of noradrenaline precursor - 1-DOPA restored the noradrenaline level in the myocardium completely after a 48-hour stimulation. Simultaneously there were noted no changes in the activity of the enzymes under study caused by the stimulation of the aortic arch. The data obtained confirmed the important role of the sympathetic nervous system and of its mediator - noradrenaline in the mechanism of the tissue metabolism regulation, whose derangement played a significant role in the development of dystrophic lesions of the heart tissue.

[Energy metabolism and myocardial function in myocardiodystrophy]

A total of 92 patients with chronic tonsilitis and cardiovascular changes were subjected to clinical observations, ECG analysis, potassium and nitroglycerine tests, and studies of the lactic acid level and creatinekinase activity as indces of myocardial metabolism. The examinations were conducted prior to and following tonsillectomy. In a majority of patients a correlation was revealed between the degree of ECG changes and the serum lactic acid level, as well as between the ECG improvement and a reduction of the lactic acid level following tonsillectomy. Three stages of tonsillogenic myocardiodystrophy were distinguished. The obtained data indicate the rationale of the used tests for the evaluation of the myocardial meabolism alterations and of the efficacy of treatment of chronic tonsillitis patients.

[Activity of energy metabolism related enzymes in the myocardium and liver following administration of large doses of noradrenaline]

The activity of the glycolytic enzymes and of the glucose-6-phosphate dehydrogenase (G-6-PDH) were compared with the content of noradrenaline in rat myocardium and the liver after the intraperitoneal injection of high doses of noradrenaline. It was shown that 24 hours after int noradrenaline injection which caused exhaustion of endogenous catecholamine supply, the lactate content and the activities of lactic dehydrogenase were increased in the myocardium; the activity of hexokinase and G-6-PDH in rat myocardium and the liver were also increased, whereas the glucokinase activity was decreased. In these experiments alterations of the enzyme activities were shown to be similar to the alterations in the dystrophic tissues in which the catecholamine content was sharply decreased. The role of the sympathetic nervous system and its mediators in the mechanism of the enzyme regulation of the energy metabolism in the myocardium and the liver is discussed.

[Prophylactic and therapeutic action of etimizol on the change in myocardial tissue metabolism in a neurogenic lesion]

The effect of aethimizol, introduced to rabbits before and after inflicting a 3-hours long extraordinary stimulation applied to the reflexogenic zone of the aortic arch, was studied. Investigations covered some aspects of energy metabolism and the level of the norepinephrine mediator in the muscle of the heart and also the functional state of the latter. Aethimizol was found to prevent shifts of the studied metabolic factors, induced by electric stimulation, and also to avert depletion of norepinephrine in the tissue of the myocardium and normalize its function.