Myocardial inotropic response of rats of different ages to extrasystolic exposures in postinfarction cardiosclerosis

The age-dependent features of the inotropic response of isolated strips of rat papillary muscles in postinfarction cardiosclerosis were studied. The rhythmic-inotropic response of the myocardium to extrasystolic eff ects was assessed in sham-operated (SO) rats and rats with established post-infarction cardiosclerosis (PICS) in the age groups of 4, 12, and 24 months (mon). It was shown that the excitability of the sarcoplasmic membrane of cardiomyocytes increases in 12-mon-old SO animals, and decreases in 24-mon-old animals relative to the group of 4-mon-old SO animals. The ability of the sarcoplasmic reticulum (SPR) of cardiomyocytes to accumulate calcium ions (Ca2+) does not depend on age. Postinfarction myocardial remodeling is accompanied by a decrease in the excitability of the sarcolemma in 4-mon-old animals and an increase in 24-mon-old animals relative to the values in SO rats of the corresponding age. At the same time, the Ca2+-accumulating ability of the SBP decreases in 4- and 12-mon-old animals, remaining unchanged in 24-mon-old animals.