Modulation of cholinergic airway reactivity and nitric oxide production by endogenous arginase activity.
Cholinergic airway constriction is functionally antagonized by agonist-induced constitutive nitric oxide synthase (cNOS)-derived nitric oxide (NO). Since cNOS and arginase, which hydrolyzes L-arginine to L-ornithine and urea, use L-arginine as a common substrate, competition between both enzymes for the substrate could be involved in the regulation of cholinergic airway reactivity. Using a perfused guinea-pig tracheal tube preparation, we investigated the modulation of methacholine-induced airway constriction by the recently developed, potent and specific arginase inhibitor N(Omega)-hydroxy-nor-L-arginine (nor-NOHA). Intraluminal (IL) administration of nor-NOHA caused a concentration-dependent inhibition of the maximal effect (E(max)) in response to IL methacholine, which was maximal in the presence of 5 microM nor-NOHA (E(max)=31.2+/-1.6% of extraluminal (EL) 40 mM KCl-induced constriction versus 51.6+/-2.1% in controls, P<0.001). In addition, the pEC(50) (-log(10) EC(50)) was slightly but significantly reduced in the presence of 5 microM nor-NOHA. The inhibition of E(max) by 5 microM nor-NOHA was concentration-dependently reversed by the NOS inhibitor N(Omega)-nitro-L-arginine methyl ester (L-NAME), reaching an E(max) of 89.4+/-7.7% in the presence of 0.5 mM L-NAME (P<0.01). A similar E(max) in the presence of 0.5 mM L-NAME was obtained in control preparations (85.2+/-9.7%, n.s.). In the presence of excess of exogenously applied L-arginine (5 mM), 5 microM nor-NOHA was ineffective (E(max)=33.1+/-5.8 versus 31.1+/-7.5% in controls, n.s.). The results indicate that endogenous arginase activity potentiates methacholine-induced airway constriction by inhibition of NO production, presumably by competition with cNOS for the common substrate, L-arginine. This finding may represent an important novel regulation mechanism of airway reactivity.
Meurs
H
H
Department of Molecular Pharmacology, University Centre for Pharmacy, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands.
Hamer
M A
MA
Pethe
S
S
Vadon-Le Goff
S
S
Boucher
J L
JL
Zaagsma
J
J
D000818:Animals; D001119:Arginase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016084:Bronchoconstriction / Q000187:drug effects; D016085:Bronchoconstrictor Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D016210:Methacholine Chloride / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013047:Specific Pathogen-Free Organisms; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
D016085:Bronchoconstrictor Agents; D004791:Enzyme Inhibitors; C404735:N(omega)-hydroxynorarginine; D016210:Methacholine Chloride; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D001119:Arginase; D019331:NG-Nitroarginine Methyl Ester