[The system of cyclic nucleotides during myocardial hyperfunction and hypertrophy in rats of various ages].

Simulation of myocardial hyperfunction and hypertrophy in rats exhibited the age- and hypertrophy step-dependent alterations in the system of cyclic nucleotides. Significant activation of the HC-cGMP system, decrease in content of cAMP and stimulation of the AC activity were detected in old animals at the emergency step. At the later steps content of cAMP and the AC stimulated activity were increased more distinctly in adult rats as compared with old animals. These alterations were responsible for age-related peculiarities of myocardial contractility at the emergency step as well as for development of hypertrophy at the later steps. The cyclase system appears to facilitate the age-related adaptation of myocardium to overloading during the old age.