[Myocardial resistance to adrenaline in rats adapted to hypoxia].

Expression of the damaging effect of adrenalin on the myocardium of rats adapted to hypoxia was studied under condition of adrenalin being injected into the integral body or in perfusion of an isolated heart. The damage was tested by the histoenzymatic reaction for the succinic dehydrogenase activity and staining for lipids. When the cardiotoxic dose (2.0 mg/kg) of adrenalin was injected intramuscularly to the adapted rats no damage of the myocardium was found, but perfusion of the isolated heart with adrenalin (20 microgram/ml) induced cardiocyte micronecrosis. The volume of these necroses was statistically less than in the isolated heart of the intact rats under analogous treatment. The difference between the sensitivity of the myocardium in vivo and in vitro indicated that in rats adapted to hypoxia the phenomenon of the myocardium protection from the damaging effect of adrenalin acted on the integral body level. An increased resistance of the myocardium proper seems to be caused by the increase of the metabolic system force during adaptation.