title: Differential effects of vasodilators on the mobilization of calcium pools during contractions of rabbit ear artery induced by noradrenaline and high potassium.
abstract: The effects of some vasodilators on the mobilization of different Ca2+ pools during contractions produced by noradrenaline and high K+ medium in rabbit ear artery has been investigated. Sodium nitrite was much more effective in antagonizing high K+-stimulated Ca2+ fluxes through the potential-dependent Ca2+ channels than noradrenaline-induced mobilization of intracellular Ca2+ stores or Ca2+ fluxes through receptor-operated channels. Papaverine was only slightly more active on contractions sustained by influx of extracellular Ca2+ (through potential-dependent channels and receptor-operated channels) than on those sustained by intracellular Ca2+. Verapamil and nifedipine were much more effective in antagonizing contractions sustained by Ca2+ entry through potential-dependent channels than through receptor-operated channels. Nifedipine was completely ineffective in antagonizing noradrenaline-induced mobilization of intracellular Ca2+ stores while verapamil had a limited inhibitory action in high concentrations. Phentolamine was equieffective in antagonizing both types of noradrenaline-induced contractions while having no effect on high K+-induced tonic contraction.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004431:Ear, External / Q000098:blood supply; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014665:Vasodilator Agents; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D010646:Phentolamine