title: Pranidipine enhances relaxation produced by endothelium-derived relaxing factor in carotid artery.
abstract: The effects of pranidipine, a novel dihydropyridine-type Ca(2+)-channel antagonist, on acetylcholine-induced endothelium-dependent relaxation were investigated in isolated carotid artery of the guinea-pig. In arteries contracted with high-K(+) solution ([K(+)](0)=28.8 mM) containing noradrenaline, the relaxation was inhibited by N(omega)-nitro-L-arginine, indicating an involvement of endothelium-derived relaxing factor. Pranidipine (10(-9)-10(-7) M) augmented the relaxation in a concentration-dependent manner. Sodium nitroprusside produced a relaxation in arteries contracted with high-K(+) solution containing noradrenaline, in an endothelium-independent manner, and the relaxation was enhanced by pranidipine. 1H-[1,2,4] oxadiazolo [4, 3-a] quinoxalin-l-one (ODQ), an inhibitor of nitric oxide-sensitive guanylate cyclase, attenuated the relaxation produced by acetylcholine or sodium nitroprusside. In the presence of ODQ, pranidipine did not enhance the acetylcholine-induced relaxation. The relaxation produced by endothelium-derived hyperpolarizing factor was inhibited by pranidipine, with no alteration of the hyperpolarization. Thus, pranidipine augments the nitric oxide-induced relaxation, possibly by enhancing the mechanisms related to cyclic GMP.
authors.affiliation: Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Koshita
authors.forename: H
authors.initials: H
authors.lastname: Takano
authors.forename: Y
authors.initials: Y
authors.lastname: Nakahira
authors.forename: H
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002339:Carotid Arteries / Q000187:drug effects* / Q000502:physiology; D004095:Dihydropyridines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D002121:Calcium Channel Blockers; D004095:Dihydropyridines; D004791:Enzyme Inhibitors; D010069:Oxadiazoles; D011810:Quinoxalines; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; C048161:pranidipine; D000109:Acetylcholine; D011188:Potassium; D009638:Norepinephrine; D007213:Indomethacin