Interaction between theophylline and ouabain in the rabbit heart: effect on (Na+ + K+)-ATPase.
In electrically stimulated rabbit ventricular strips, theophylline (0.3-30 mM) antagonized the increased contractility produced by ouabain (0.8 microM). Initial velocity of specific [3H]ouabain binding to homogenates prepared from the muscle strips was used to determine the fraction of binding sites occupied by ouabain. Theophylline decreased the binding of ouabain to (Na+ + K+)-ATPase. It is concluded that the effect of theophylline on ouabain-induced positive inotropism may be mediated by decreased ouabain binding to (Na+ + K+)-ATPase.
D000818:Animals; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000201:enzymology*; D010042:Ouabain / Q000037:antagonists & inhibitors*; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013268:Stimulation, Chemical; D013806:Theophylline / Q000494:pharmacology*
D010042:Ouabain; D013806:Theophylline; D000254:Sodium-Potassium-Exchanging ATPase