Bethanidine increases one type of potassium current and relaxes aortic muscle.
Using a whole-cell voltage-clamp technique, we identified two time- and voltage-dependent K+ currents: an early outward rectifier and a delayed outward rectifier in single vascular smooth muscle cells of rabbit aorta in culture. About 90% of the single cells tested showed a predominant delayed outward K+ current type. Both K+ currents were decreased by tetraethylammonium. In contrast, bethanidine sulphate (10(-4)M), a pharmacological analog of the cardiac antifibrillatory drug, bretylium tosylate, decreased the early outward K+ current, increased the delayed rectifier K+ current type, and hyperpolarized the resting membrane potential. Bethanidine was found to relax vascular smooth muscle. The vasodilatory effect of bethanidine is associated with the activation of a K+ current that is probably involved in keeping the membrane potential at the resting state, thereby depressing the excitability of the aortic vascular smooth muscle.
Bkaily
G
G
Department of Physiology and Biophysics, Faculty of Medicine, Université de Sherbrooke, Qué., Canada.
Caillé
J P
JP
Payet
M D
MD
Peyrow
M
M
Sauvé
R
R
Renaud
J F
JF
Sperelakis
N
N
D000818:Animals; D001627:Bethanidine / Q000494:pharmacology*; D002478:Cells, Cultured; D004594:Electrophysiology; D006146:Guanidines / Q000494:pharmacology*; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D011188:Potassium / Q000502:physiology*; D011817:Rabbits; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D006146:Guanidines; D013757:Tetraethylammonium Compounds; D011188:Potassium; D001627:Bethanidine