Influence of disopyramide, compared with procainamide and quinidine, on isolated dog arteries in response to transmural stimulation and norepinephrine.

In helically cut strips of dog cerebral, coronary, and mesenteric arteries contracted with prostaglandin (PG) F2 alpha, disopyramide phosphate produced moderate contractions that were unaffected by phentolamine, chlorpheniramine, cinanserin, or aspirin. Procainamide and quinidine elicited only a slight contraction. Mesenteric arterial strips contracted with norepinephrine slightly contracted in response to disopyramide but significantly relaxed with procainamide and quinidine. The contractile response of mesenteric arterial strips to transmural electrical stimulation was attenuated by high concentrations (5 x 10(-5) M) of disopyramide or procainamide and by low concentrations of quinidine. Disopyramide-induced attenuation was greater in the response to high-frequency stimulation. Disopyramide at high concentrations potentiated the contractile response of mesenteric arteries to norepinephrine and tyramine, while, in contrast, procainamide and quinidine shifted the dose-response curve for norepinephrine to the right. Treatment with procainamide and quinidine, but not with disopyramide, protected alpha-adrenoceptors from persistent blockade by phenoxybenzamine; quinidine was far more effective than procainamide. It may be concluded that disopyramide possesses a nonspecific vasoconstricting action but not an alpha-adrenoceptor blocking property, whereas quinidine and procainamide show a reversible, competitive alpha-adrenoceptor antagonism. Different hemodynamic actions of these antiarrhythmics in situ appear to be related to such contrasting effects on arterial smooth muscle.