STUDIES ON THE ACTION OF NYSTATIN ON CULTURED RAT MYOCARDIAL-CELLS AND CELL-MEMBRANES, ISOLATED RAT HEARTS, AND INTACT RATS

The action of nystatin, a polyene antibiotic [and clinically useful antifunal drug], was studied in rat myocardial cells, isolated rat hearts and intact rats. Myocardial cells responded to 10 and 25 .mu.g nystatin/ml with arrhythmias that could be minimized by elevated concentrations of K+ and Mg2+ or reversed by washing the cells. Similarly, the isolated heart responded to 100 .mu.g nystatin/ml with arrhythmias that could be tempered by addition of elevated concentrations of K+ and Mg2+. The i.v. injection of the drug caused heart failure in intact animals at the 4-mg/kg dose level. At the subcellular level, nystatin made the myocardial cell membranes more rigid, as measured by electron spin resonance spectrometry. These findings indicate a parallel between physicochemical changes caused by nystatin in the myocardial cell membrane and the biological changes caused by this drug in myocardial cells, isolated heart and of the intact animal.