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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.

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.

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.

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.