Vasylenko M. Hypoxic and hyperthermic preconditioning of the myocardium in rats: age-related peculiarities.

The study is aimed at estimation of age-related peculiarities of development of the late cardioprotection state induced by the influences of acute hypoxic hypoxia and acute hyperthermia and at identification of possible mechanisms of these types of preconditioning. Novel modes of hypoxic and hyperthermic sessions inducing the effect of late preconditioning of the myocardium in rats have been developed. Modifications in the cardiodynamics and biochemical and morphological characteristics of the myocardium related to this state are described; special attention is paid to the role of NOS in the development of the preconditioning effect. It was found that the levels of iNOS-expression in the myocardium of young and mature adult rats are dissimilar (in young animals, this index is twofold higher than that in mature ones). The levels of expression of this enzyme in different heart ventricles also differ from each other (in the right ventricle, this index is higher than that in the left one; the difference is 80% and 20 % in young and mature animals, respectively). The iNOS expression in the myocardium of young and mature rats changes after acute hypoxic hypoxia in different directions: expression of this enzyme increases in the former animals and drops in the latter ones. It is concluded that a general age group of adult rats should be divided into the subgroups of adult young and adult mature animals. These subgroups demonstrate significant specificities of a number of physiological characteristics (dissimilar reactivity of the myocardium in particular). Key words: hypoxia, hyperthermia, late preconditioning, cardioprotection, ischemia of the myocardium, age related peculiarities of preconditioning.