[Mechanisms of development of cardiac insufficiency in old age]

Tests conducted with adult (8--10 months) and old (26--28 months) rats brought evidence that in ageing the cardiac ejection, dp/dt max, contractility index, the ATP concentration, that of creatinophosphate, glycogen, pyruvate decline, the phosphorylation coefficient, the lactate content increase, while the level of water-soluble proteins and collagen diminishes and that of water-insoluble ones decreases. In adult rats hemodynamics and myocardial contractility change but unsignificantly on the 4--6th day after coarctation of the aorta, whereas in the old ones there occur functional and metabolic alterations in the heart that are indicative of a developing cardiac insufficiency. The age-specific differences persist also on the 14--16th day following coarctation of the aorta. During these periods the weight of the heart, the content of the myofribrillary proteins and collagen are on the rise, whereas in the old ones the weight of the heart remains unchanged and the level of water-soluble protein drops. Changes in the properties of the actomyosin complex, disruption of the calcium pump, shifts in the system of the energy generation, limitation of potential possibilities incident to the systems of protein biosynthesis in the myocardial cell, all this leads to the development of cardiac incompetence following loading in old age.