title: Inhibition of ouabain-induced increase in Na content of cultured myocardial cells by quinidine and procainamide.
abstract: Addition of ouabain caused gradual increases of both the Na content of cultured myocardial cells and the rate of Ca++ uptake by the cells. Ouabain-induced irregular beating of the cells (ouabain toxicity) appeared to develop when the Na content and the rate of Ca++ uptake exceeded about 1.5 and 2.0 times, respectively, the normal levels. Quinidine and procainamide prevented ouabain-induced increases of the Na content and the rate of Ca++ uptake as well as ouabain-induced toxicity. The problem of how quinidine and procainamide counteract the effects of ouabain was then studied. Quinidine and procainamide did not affect the Na+-Ca++ exchange activity. Na+,K+-adenosine triphosphatase activity, Na+-pumping out activity or ouabain-binding activity of myocardial cells, but inhibited passive Na+ influx, which is achieved by a simple diffusion system. From these observations, it is suggested that inhibition by quinidine or procainamide of passive Na+ influx indirectly prevents ouabain-induced increase in the intracellular Na content of myocardial cells and that this presumably explains at least in part the inhibitory effect of quinidine and procainamide on ouabain-induced irregular beating.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005333:Fetus; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010042:Ouabain / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D011342:Procainamide / Q000494:pharmacology*; D011784:Quail; D011802:Quinidine / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011802:Quinidine; D011342:Procainamide; D002118:Calcium