Comparative studies of cardiodepressant drugs on contraction dynamics and electrophysiological parameters of cardiac tissues at pH 7.4 and 9.
The effects of propranolol, amethocaine (tetracaine), lignocaine (lidocaine), procaine and benzocaine on force of contraction and action potential parameters of guinea-pig left atria and papillary muscles have been investigated at pH 7.4 and 9. All the drugs decreased the force of contraction of both preparations. Their biological activities correlated with their lipid/buffer partition coefficients and with their ability to change the surface potential of liposomes. The sequence of activities is as follows: propranolol greater than amethocaine greater than lignocaine greater than benzocaine greater than procaine. Uncharged benzocaine had no effect on the liposome surface charge. Biological and physicochemical effects obtained at pH 9 were higher than those observed at pH 7.4. Action potential amplitude and Vmax were decreased by all the drugs except benzocaine. At pH 9, the action potential duration was generally shortened, except by amethocaine and procaine; both caused a prolongation of the action potential at 90% repolarization.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008081:Liposomes; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology; D012032:Refractory Period, Electrophysiological / Q000187:drug effects; D013329:Structure-Activity Relationship
D000889:Anti-Arrhythmia Agents; D008081:Liposomes; D011433:Propranolol