The studies concerned age-dependent peculiarities of the vasopressin effect on the hemodynamics and tone of the coronary vessels in dogs, the contraction of the isolated vascular strip in rats, and the hemodynamic and ECG indices in rabbits and in rats. The data obtained indicate the great sensitivity of old vessels to vasopressin. In aging, both humans and animals show a rise of vasopressin concentration in the blood. Age-dependent differences of the vasopressin effect on the kallikrein-kinin system, adenosine metabolism, the contents of prostaglandins and cyclic AMP have been established. High sensitivity to vasopressin in combination with its increased concentration in the blood is an important factor that contributes to the development of arterial hypertension and ischemic heart disease.

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Experiments on isolated hearts from adult and old rats have proved an age-dependent decrease in the resistance of contractile function and cardiac rhythm to ischemia and reperfusion. The restriction of coronary flow by 70% produced significant changes in various links of the Ca²⁺ transport system (an increase in sarcolemmal permeability for Ca²⁺ and a decrease in Ca²⁺-accumulating capacity of sarcoplasmic reticulum included). These changes, more marked in old animals, seemed to play an important role in the mechanisms of disturbances in cardiac function following coronary insufficiency.

Experiments with animals with various species-specific life span (rats, rabbits, cats, dogs) and different models (in situ heart, isolated perfused heart, isolated papillary muscle) have proved the reduction of functional capacity of the ageing heart. Diversely directional age-dependent shifts have been established involving myocardial Ca²⁺ transport system, i.e. an increase in the rate of Na⁺-Ca²⁺ exchange and passive Ca²⁺ transport across sarcolemma and a decrease in its Ca²⁺-binding capacity and a decrease in Ca²⁺ accumulation by sarcoplasmic reticulum and mitochondria (Ca²⁺ uptake). The experiments revealed a decrease in the Ca²⁺ ATPase myosin activity in the myocardium of aged animals and absence of age changes in the K⁺ ATPase activity. The findings obtained suggest that the development in the cardiac contractile function disorders in ageing largely depends on the age-related changes in the Ca²⁺ transport system.

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