[Comparative analysis of the changes in myocardial electrical and contractile activity in rats exposed to rubomycin and its nitroxyl derivative].

A comparative analysis was performed of changes in the contractile and electrical activity of the rat myocardium in experiments on isolated papillary muscles, obtained 2-2.5 months after the discontinuation of chronic administration of rubomicin in 0.7 mg/kg and ruboxil in 3 mg/kg dose to the animals. It is shown that rubomicin decreases the maximal rate of growth of the anterior potential of action and in a greater degree than ruboxil inhibits the contractile activity of papillary muscles. The preparations had a contrary influence on the rhythmoinotropic relations in the rat myocardium. This difference might be connected with the ability of rumobimicin to block and of ruboxil to stimulate Na-Ca metabolism. The participation of these mechanisms in the process of development of cardiotoxicity of antracycline antibiotics is discussed.