The influence of adrenaline on contractility and excitability of myocardium of rat right ventricle depending on phases of the estrous cycle and pregnancy

Abstract

Investigated the contractile activity of 34 myocardium strips of right ventricular of 17 nonpregnant rats, including with estrogen (9) and progesterone (8) background, and 17 pregnant rats — at the early (5–10 days; n = 7), middle (11–18 days; n = 7) and late (19–21 days; n = 3) stages. Contractions caused by electrostimuls (5 ms, 20 B, 1 Hz), and their registration was performed using the force transducer. Adrenoreactivity of strips were evaluated by the pattern of inotropic and batmotropic effects of adrenaline (10-9–10-5 g/ml). It has been established that contractility of myocardium is not changed during the estrous cycle. In pregnancy, it does not increase, and even decreases, which is typical for middle and late stages. Adrenoreactivity of myocardium, according to the inotropic effect of adrenaline, did not depend on the phase of the estrous cycle (PhEC), but depended on the presence of pregnancy — in early stages it remained relatively high, and in the middle and late stages — decreased. Excitability of intactmyocardium did not depend on PhEC and the presence of pregnancy. Adrenaline showed positive batmotropic effect. Its expression was dependent on the PhEC (it decreases with the dominance of progesterone background) and the presence of pregnancy (in early stage it increases, and in the middle and late stages — it decreases). It is assumed that changes of adrenoreactivity of the myocardium of the rat right ventricle during pregnancy are due by increasing of the expression of alpha1-, beta2- and beta3-adrenoceptors. Refs 58. Figs 5. Table 1.