title: Effect of Rb+ on cromakalim-induced relaxation and ion fluxes in guinea pig trachea.
abstract: The effects of cromakalim, verapamil and salbutamol have been examined in guinea pig trachealis smooth muscle in both Krebs physiological salt solution and Krebs solution where K+ has been replaced by Rb+. Cromakalim-induced relaxation in the presence of Rb+ was reduced in extent and became transient, whilst the relaxation response to verapamil was enhanced and that to salbutamol unaffected. The transient relaxation occurring in Rb+ was blocked by quinidine and glibenclamide. The presence of extracellular Rb+ also prevented cromakalim-stimulated efflux of both 86Rb+ and 42/43K+. There was, however, no effect on cromakalim-stimulated 86Rb+ uptake. It is proposed that cromakalim is opening two populations of potassium channel in guinea pig tracheal smooth muscle, one of which is susceptible to blockade by Rb+ and one of which is not. The latter channel appears to play the dominant role in cromakalim-stimulated uptake, and is responsible for the transient relaxation response in the presence of rubidium, whilst the former is responsible for the maintained relaxation.
authors: SmithKline Beecham Pharmaceuticals, Epsom, Surrey, UK.
authors: K A
authors: KA
authors: Foster
authors: J R
authors: JR
authors: Arch
authors: P N
authors: PN
authors: Newson
authors: D
authors: D
authors: Shaw
authors: S G
authors: SG
authors: Taylor
mesh_terms: D000420:Albuterol / Q000494:pharmacology; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology*; D001993:Bronchodilator Agents / Q000494:pharmacology*; D019806:Cromakalim; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology*; D012413:Rubidium / Q000494:pharmacology*; D012414:Rubidium Radioisotopes; D014132:Trachea / Q000187:drug effects / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D001578:Benzopyrans; D001993:Bronchodilator Agents; D011758:Pyrroles; D012414:Rubidium Radioisotopes; D019806:Cromakalim; D014700:Verapamil; D007545:Isoproterenol; D012413:Rubidium; D000420:Albuterol; D011188:Potassium