Nitric oxide synthesis by tracheal smooth muscle cells by a nitric oxide synthase-independent pathway.
Nitric oxide (NO) is known to be synthesized from L-arginine in a reaction catalyzed by NO synthase. Liver cytochrome P-450 enzymes also catalyze the oxidative cleavage of C==N bonds of compounds containing a -C(NH2)==NOH function, producing NO in vitro. The present study was designed to investigate whether there was evidence of a similar pathway for the production of NO in tracheal smooth muscle cells. Formamidoxime (10(-2) to 10(-4) M), a compound containing -C(NH2)==NOH, relaxed carbachol-contracted tracheal rings and increased intracellular cGMP in cultured tracheal smooth muscle cells, whereas L-arginine had no such effect. NO was detectable in the medium containing cultured tracheal smooth muscle cells when incubated with formamidoxime. Ethoxyresorufin (10(-7) to 10(-4) M), an alternate cytochrome P-450 substrate, inhibited formamidoxime-induced cGMP accumulation as well as tracheal ring relaxation in cultured tracheal smooth muscle cells. The NO synthase inhibitors Nomega-nitro-L-arginine (10(-3) M) and NG-monomethyl-L-arginine (10(-3) M) had no effect on formamidoxime-induced cGMP accumulation. These results suggest that NO can be synthesized from formamidoxime in tracheal smooth muscle cells, presumably by a reaction catalyzed by cytochrome P-450.
Jia
Y
Y
Meakins-Christie Laboratories, McGill University, and Cystic Fibrosis Laboratory, Montreal Chest Hospital, Montreal, Quebec, Canada H2X 2P2.
Zacour
M
M
Tolloczko
B
B
Martin
J G
JG
D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006898:Hydroxylamines / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D019335:Nitroarginine / Q000494:pharmacology*; D010078:Oxazines / Q000494:pharmacology; D010091:Oximes; D051381:Rats; D011917:Rats, Inbred Lew; D014132:Trachea / Q000187:drug effects / Q000502:physiology*; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D000634:Aminoquinolines; D004791:Enzyme Inhibitors; D006898:Hydroxylamines; D010078:Oxazines; D010091:Oximes; D019335:Nitroarginine; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C007649:ethoxyresorufin; C001250:formamidoxime; D003577:Cytochrome P-450 Enzyme System; C041715:6-anilino-5,8-quinolinedione; D019001:Nitric Oxide Synthase