Old rats exhibited lower amplitude and reduced rate of isometric tension development, longer action potential duration, and significantly longer CaT decay time compared to young rats.
Aging in rats is associated with altered length-dependent regulation of myocardial contractility, characterized by reduced isometric tension and prolonged calcium transient decay.
The issue of cardiovascular regulation during aging receives insufficient attention despite its high social significance. The common pathogenesis of cardiovascular regulation disorders in experimental animals and elderly individuals makes it relevant to study the mechanisms of myocardial contractility regulation in comparative experiments on laboratory animals of different ages. To identify the specific changes in length-dependent mechanisms regulating the contractility of healthy myocardium during aging, the characteristics of mechanical and electrical activity, as well as the kinetics of intracellular calcium ion concentration (calcium transient, CaT), were assessed in single contractions of the right ventricular myocardium in groups of young (1 month) and old (2.5 years) rats. The experiments were carried out on the right ventricular trabeculae of the male Wistar rat hearts. The indices of mechanical tension, CaT, and action potentials (APs) were recorded in an isometric contraction mode under varying degrees of stretching. It was found that the myocardium of old animals is characterized by a lower amplitude of isometric tension, a reduced rate of isometric tension development, and a longer AP duration compared to young animals. For the first time, age-related features of length-dependent changes were detected upon superposition of CaT curves obtained at different preloads of the ventricular myocardium. In old rats, the CaT decay time at 30% of the amplitude was significantly longer than in young animals. Our original method of CaT difference curves revealed the influence of preload on calcium ion kinetics in cardiomyocytes of multicellular ventricular myocardial strips in rats of different ages. Specifically, the relative amplitude and area of segment III of the CaT difference curves were significantly greater in young animals compared to old ones.
Lisin et al. (Tue,) conducted a other in Healthy myocardium during aging. Old age (2.5 years) vs. Young age (1 month) was evaluated on Characteristics of mechanical and electrical activity, and kinetics of intracellular calcium ion concentration (CaT) under varying degrees of stretching. Old rats exhibited lower amplitude and reduced rate of isometric tension development, longer action potential duration, and significantly longer CaT decay time compared to young rats.