Calcium-dependent toxic effects of digoxin in isolated myocardial preparations.
On isolated guinea-pig papillary muscles as well as on electrically driven atria digoxin was infused into the bath fluid until cardiac arrest occurred. The concentration of digoxin which caused standstill is defined as the toxic one. The toxicity was determined under various Ca2+-concentrations. On the papillary muscle the increase of extracellular Ca2+ from 0.9 to 7.2 mM increased the toxicity of digoxin, i.e. significantly diminished its toxic concentrations. Likewise, on electrically driven atria an increase of Ca2+ from 0.45 to 7.2 mM increased the toxicity of digoxin. These results demonstrate that with regard to the toxicity Ca2+ and digoxin act synergistically.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D004077:Digoxin / Q000494:pharmacology*; D004357:Drug Synergism; D004558:Electric Stimulation; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006323:Heart Arrest / Q000139:chemically induced; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects
D004077:Digoxin; D002118:Calcium