Differential effects of quinidine on transmembrane action potentials of normal and infarcted canine Purkinje fibers.
Fourteen days after proximal ligation of the left anterior descending coronary artery (LAD) of mongrel dogs, the effects of quinidine on action potentials of normal and infarcted Purkinje fibers were evaluated. The concentration-dependent (10(-7)-3 x 10(-5) M) and frequency-dependent (1 and 3 Hz) actions of quinidine were evaluated by the following parameters: maximum upstroke velocity (Vmax), action potential duration at 50 and 95% repolarization (APD50, APD95), effective refractory period (ERP), resting membrane potential (RMP), and action potential amplitude (APA). Quinidine reduced Vmax in normal and abnormal Purkinje fibers in a concentration- and frequency-dependent manner; these effects were more pronounced in infarcted tissue. The APD50 was shortened significantly at 1 Hz in noninfarcted Purkinje fibers, whereas in infarcted Purkinje fibers quinidine had no effect on APD50. The APD95 was not significantly altered by quinidine in normal Purkinje fibers; in infarcted areas APD95 was significantly prolonged at 1 and 3 Hz. The effective refractory period (ERP) was prolonged in normal and infarcted Purkinje fibers, these effects were more marked in ischemically damaged fibers. No effects were observed on resting membrane potential (RMP). APA was reduced significantly after quinidine at 1 and 3 Hz; there was no difference between normal and infarcted tissue. These data indicate a differential effect of quinidine in normal and infarcted Purkinje fibers which may be an important mechanism of action of quinidine in infarcted tissue.
Montero
M
M
Department of Cardiology, University of Heidelberg, Germany.
Beyer
T
T
Schmitt
C
C
Kübler
W
W
Brachmann
J
J
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects / Q000503:physiopathology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009203:Myocardial Infarction / Q000503:physiopathology*; D011690:Purkinje Fibers / Q000187:drug effects* / Q000503:physiopathology; D011802:Quinidine / Q000494:pharmacology*
D011802:Quinidine