title: KATP channels contribute to beta- and adenosine receptor-mediated pulmonary vasorelaxation.
abstract: ATP-sensitive K+ (KATP) channels have been implicated in the regulation of vasomotor tone in aortic, mesenteric, and pulmonary vascular smooth muscle. Several investigators have described an association between KATP channels and isoproterenol (Iso)-stimulated relaxation responses. To study the relationship between receptor-dependent pulmonary vasorelaxation and KATP channels, we examined the response to agonists that generate adenosine 3',5'-cyclic monophosphate at two distinct levels of the signal transduction pathway after inhibition or activation of KATP channels in isolated rat pulmonary artery rings. Cumulative concentration responses to beta-adrenergic receptor stimulation (Iso), purinergic receptor stimulation [adenosine (Ado)], and direct stimulation of adenylate cyclase [forskolin (FSK)] were studied with and without concurrent inhibition of KATP channels (glibenclamide or tolbutamide). In addition, the effect of direct KATP channel activation (cromakalim) on the response to beta-adrenergic and purinergic receptor stimulation was determined. Last, we investigated the influence of KATP channel inhibition on endothelium-dependent and -independent mechanisms of pulmonary vasorelaxation linked to guanosine 3',5'-cyclic monophosphate production. KATP channel inhibition impaired the response to Iso and Ado. Activation of KATP channels caused a leftward shift in the dose responses of Iso and Ado, with a significant decrease in the 50% effective concentration for each agent. KATP channel inhibition did not impair the pulmonary arterial vasorelaxation response to FSK, acetylcholine, or sodium nitroprusside. KATP channels appear to contribute to beta-adrenergic and purinergic receptor-stimulated vasorelaxation in rat pulmonary arteries.
authors.affiliation: Department of Surgery, University of Colorado, Denver 80262, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Sheridan
authors.forename: R C
authors.initials: RC
authors.lastname: McIntyre
authors.forename: D R
authors.initials: DR
authors.lastname: Meldrum
authors.forename: D A
authors.initials: DA
authors.lastname: Fullerton
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000109:Acetylcholine / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D019806:Cromakalim / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D054086:KATP Channels; D007700:Kinetics; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000502:physiology*; D014044:Tolbutamide / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D054086:KATP Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011943:Receptors, Adrenergic, beta; D018047:Receptors, Purinergic P1; C092520:uK-ATP-1 potassium channel; D019806:Cromakalim; D009599:Nitroprusside; D005576:Colforsin; D014044:Tolbutamide; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D000241:Adenosine; D007545:Isoproterenol; D000109:Acetylcholine; D005905:Glyburide