Comparison of effects of a potassium channel opener BRL34915, a specific potassium ionophore valinomycin and calcium channel blockers on endothelin-induced vascular contraction.
The effects of a potassium (K+) channel opener BRL34915 and a specific K+ ionophore valinomycin on vasoconstriction induced by endothelin (ET) were compared with those of calcium (Ca2+) channel blockers, nicardipine and verapamil, using helical strips from rat thoracic aorta. ET induced potent and persistent contraction in control solution and similar but smaller contraction in Ca2+-free solution. BRL34915 and valinomycin inhibited the ET-induced contraction dose-dependently in control solution, but not in Ca2+-free solution. The ET-induced contraction was also inhibited by nicardipine and verapamil, though less strongly. On the other hand, high K+ (35 mM)-induced vasoconstriction was strongly inhibited by nicardipine and verapamil, but not by BRL34915 or valinomycin. These results support the idea that the extracellular Ca2+-dependent component of the ET-induced contraction may be mediated by Ca2+ influx by a route other than voltage-dependent Ca2+-channels.
Kim
S
S
Department of Geriatric Medicine, Osaka University Medical School, Japan.
Morimoto
S
S
Koh
E
E
Miyashita
Y
Y
Ogihara
T
T
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D001578:Benzopyrans / Q000494:pharmacology*; D019806:Cromakalim; D004533:Egtazic Acid / Q000494:pharmacology; D016232:Endothelins; D004730:Endothelium, Vascular / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009529:Nicardipine / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects*; D011758:Pyrroles / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014634:Valinomycin / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology*
D001578:Benzopyrans; D016232:Endothelins; D010455:Peptides; D015221:Potassium Channels; D011758:Pyrroles; D014665:Vasodilator Agents; D019806:Cromakalim; D014634:Valinomycin; D004533:Egtazic Acid; D014700:Verapamil; D009529:Nicardipine; D011188:Potassium