Effect ofRhodiola rosea on the resistance of isolated heart from stressed rats to ischemic and reperfusion damage

Abstract

Experiments on isolated hearts from rats pretreated with Rhodiola rosea and subjected to combined cooling and immobilization show that this adaptogen improves the resistance of the myocardium to ischemic and reperfusion damage and exerts a membrane-stabilizing effect.Key Words: cooling; creatine phosphokinase; contractility; isolated heart," Rhodiola roseaIn 1957, H. Selye pointed out the possibility of damag e to the heart induced by cold stress [7]. Moreover, it is well known that fall of outdoor temperature considerably increases the incidence of myocardial infarction [6,8]. Under real conditions cooling is usually combined with the influence of other stress factors which can potentiate its adverse effects. However, the effect of cooling in combination with other stress factors has not yet been studied.Our previous experiments showed that acute cooling of albino rats decreases myocardial contractility in vitro, while pretreatment with Rhodiola rosea extract (RRE) prevents these disturbances [1]. However, possible mechanisms of the cardioprotective effects of Rhodiola rosea detected by us under conditions of cold and psychoemotional stress and in acute myocardial ischemia [3] remain unclear.The aim of the present study was to evaluate the effect of the adaptogen RRE on the resistance of isolated heart from rats exposed to a combination of low temperature and immobilization to the damaging effect of total ischemia and reperfusion. Department of Experimental Cardiology, Institute of Cardiology, Siberian Division of the Russian Academy of Medical Sciences, Tomsk MATERIALS AND METHODSExperiments were carried out on 36 Wistar male rats weighing 200-250 g. The rats were divided into 3 groups, 10-12 animals in each. Group l rats were stress-control. Group 2 rats were daily treated with adaptogen preparation RRE for 8 days in a dose of 1 ml/kg per os. Control group 3 comprised intact rats. A combination of acute cooling and immobilization was used as a model of stress: the rats were immobilized in supine position for 4 h at 5~Further experiments were carried out on rat hearts isolated by the Langendorff method [5]. The hearts were perfused with Krebs--Henseleit solution saturated with carbogen at 37~After a 15-min adaptation to perfusion [5], the hearts were subjected to a 45-rain total normothermal ischemia followed by a 60-rain repel-fusion. In all series, the contractile function of perfused heart was assessed in isotonic regime under a constant load of 5 g, and coronary flow was measured. The amplitude of contractions and changes in the heart diastolic length (contrac= ture) were calculated. Diastolic length was measured from the zero line 0.5 mm below diastolic fragment Of the contraction--relaxation curve. The damage to cardiomyocyte sarcolemma was assessed from creatine phosphokinase (CPK) activity in perfusate using corn-