Comparison of Ca2+ channel inhibitory effects of cibenzoline with verapamil on guinea-pig heart.
1. Cibenzoline, a class 1 antiarrhythmic drug, was studied on the effects upon the myocardial slow inward Ca2+ current (ICa) and the contractile force, and was compared with verapamil. 2. In voltage-clamp experiments with guinea-pig ventricular myocytes, cibenzoline caused a concentration-related inhibition of ICa (IC50 = 30 microM), whereas verapamil exerts a stronger effect (IC50 = 0.6 microM). 3. Cibenzoline also produced a concentration-related decrease in contractile force of isolated papillary muscle preparation (IC50 = 30 microM), while IC50 of verapamil was 0.8 microM. 4. Although the myocardial Ca2+ channel blocking effect of cibenzoline is about 1/50 compared to verapamil, cibenzoline possesses an inhibitory action on Ca2+ channel as well as on Na+ channel.
Matsuoka
S
S
1st Department of Internal Medicine, Tottori University School of Medicine, Yonago, Japan.
Nawada
T
T
Hisatome
I
I
Miyamoto
J
J
Hasegawa
J
J
Kotake
H
H
Mashiba
H
H
D000818:Animals; D002121:Calcium Channel Blockers; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects*; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology; D010210:Papillary Muscles / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D007093:Imidazoles; D014700:Verapamil; C032151:cifenline