Multiple mechanisms of vascular smooth muscle relaxation by the activation of proteinase-activated receptor 2 in mouse mesenteric arterioles.
1. Activation of PAR2 in second-order mesenteric arteriole (MA) rings from C57BL/6J, NOS3 (-/-) and PAR2 (-/-) mice was assessed for the contributions of NO, cyclo-oxygenases, guanylyl cyclase, adenylyl cyclase, and of K(+) channel activation to vascular smooth muscle relaxation. 2. PAR2 agonist, SLIGRL-NH(2) (0.1 to 30 microM), induced relaxation of cirazoline-precontracted MA from C57BL/6J and NOS3 (-/-), but not PAR2 (-/-) mice. Maximal relaxation (E(max)) was partially reduced by a combination of L-(G)N-nitroarginine methyl ester (L-NAME), 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and indomethacin. An ODQ/L-NAME/indomethacin resistant relaxation was also caused by trypsin (30 nM) in PAR2 (+/+), but not in PAR2 (-/-) mice. Relaxation was endothelium-dependent and inhibited by either 30 mM KCl-precontraction, or pretreatment with apamin, charybdotoxin, and their combination; iberiotoxin did not substitute for charybdotoxin nor did scyllatoxin substitute fully for apamin. 3. Tetraethylammonium (TEA), glibenclamide, tetrodotoxin, 17-octadecynoic acid, carboxy-2-phenyl-4,4,5,5,-tetramethyl-imidazoline-1-oxyl-3-oxide, SQ22536, carbenoxolone, arachidonyl trifluoromethyl ketone, 7-nitroindazole, N-(3-(aminomethyl)benzyl)acetamidine (1400W), N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulfonamide (NS-398) and propanolol did not inhibit relaxation. 4-aminopyridine significantly increased the potency of SLIGRL-NH(2). A combination of 30 microM BaCl(2) and 10 microM ouabain significantly reduced the potency for relaxation, and in the presence of L-NAME, ODQ and indomethacin, E(max) was reduced. 4. We conclude PAR2-mediated relaxation of mouse MA utilizes multiple mechanisms that are both NO-cGMP-dependent, and -independent. The data are also consistent with a role for endothelium-dependent hyperpolarization of vascular smooth muscle that involves the activation of an apamin/charybdotoxin-sensitive K(+) channel(s) and, in part, may be mediated by K(+).
McGuire
John J
JJ
Smooth Muscle Research Group, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1. mcguire@ucalgary.ca
Hollenberg
Morley D
MD
Andrade-Gordon
Patricia
P
Triggle
Chris R
CR
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001685:Biological Factors / Q000494:pharmacology; D006152:Cyclic GMP / Q000502:physiology; D016861:Cyclooxygenase Inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology; D006162:Guanylate Cyclase; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D009842:Oligopeptides / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D044464:Receptor, PAR-2; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors; D018179:Receptors, Thrombin / Q000378:metabolism*; D000071756:Soluble Guanylyl Cyclase
D001685:Biological Factors; D016861:Cyclooxygenase Inhibitors; D020030:Nitric Oxide Donors; D009842:Oligopeptides; D026902:Potassium Channel Blockers; D044464:Receptor, PAR-2; D018160:Receptors, Cytoplasmic and Nuclear; D018179:Receptors, Thrombin; C067410:endothelium-dependent hyperpolarization factor; C112356:seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP; D000109:Acetylcholine; D011188:Potassium; D019331:NG-Nitroarginine Methyl Ester