title: Responses of cultured heart cells to procainamide and lignocaine.
abstract: The effects of procainamide and lignocaine, in concentrations from 10(-6) to 10(-2) mol.litre(-1), on the Na influx and contraction frequency of cultured heart cells were studied. Both drugs produced a prompt, dose-dependent reduction in Na influx which was significant (P less than 0.01) for all concentrations tested. Lignocaine affected only that portion of the Na influx which was also verapamil-sensitive, whereas procainamide suppressed in addition, the verapamil-insensitive influx. In addition both drugs produced a concomitant decrease in the spontaneous contraction frequency of the cells. A close linear correlation (r = 0.99) between verapamil-sensitive Na influx and contraction frequency, in the presence of both procainamide and lignocaine was found. From this, and previous studies indicating a dependency of contraction frequency on the inward verapamil-sensitive Na influx, it is suggested that the drugs modify the automaticity of this preparation by a primary influence on membrane Na exchange.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006321:Heart / Q000187:drug effects*; D008012:Lidocaine / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism; D011342:Procainamide / Q000494:pharmacology*; D051381:Rats; D012964:Sodium / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D008012:Lidocaine; D012964:Sodium; D014700:Verapamil; D011342:Procainamide