Enhancement of the toxic effects of veratrine on guinea-pig atrium by threshold inotropic doses of ouabain.
Isolated atria of guinea-pigs were treated with veratrine until the initial signs of toxicity were seen. Ouabain was then added cumulatively, starting with a threshold inotropic concentration, 50 nM, until the tissue became dysrhythmic. It was found that a concentration of ouabain which by itself gave a positive inotropic effect of only 3%, significantly enhanced the toxicity of veratrine. Veratrine had no effect on the (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase) enzyme isolated from guinea-pig ventricle. The conclusion drawn is that at threshold inotropic concentrations of ouabain it is likely that the (Na+ + K+)-ATPase is inhibited rather than stimulated.
D000818:Animals; D003864:Depression, Chemical; D004357:Drug Synergism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013997:Time Factors; D014702:Veratrine / Q000633:toxicity*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D014702:Veratrine