title: Receptor-mediated activation of nitric oxide synthesis by arginine in endothelial cells.
abstract: Arginine contains the guanidinium group and thus has structural similarity to ligands of imidazoline and alpha-2 adrenoceptors (alpha-2 AR). Therefore, we investigated the possibility that exogenous arginine may act as a ligand for these receptors in human umbilical vein endothelial cells and activate intracellular nitric oxide (NO) synthesis. Idazoxan, a mixed antagonist of imidazoline and alpha-2 adrenoceptors, partly inhibited L-arginine-initiated NO formation as measured by a Griess reaction. Rauwolscine, a highly specific antagonist of alpha-2 AR, at very low concentrations completely inhibited NO formation. Like L-arginine, agmatine (decarboxylated arginine) also activated NO synthesis, however, at much lower concentrations. We found that dexmedetomidine, a specific agonist of alpha-2 AR was very potent in activating cellular NO, thus indicating a possible role for alpha-2 AR in L-arginine-mediated NO synthesis. D-arginine also activated NO production and could be inhibited by imidazoline and alpha-2 AR antagonists, thus indicating nonsubstrate actions of arginine. Pertussis toxin, an inhibitor of G proteins, attenuated L-arginine-mediated NO synthesis, thus indicating mediation via G proteins. L-type Ca(2+) channel blocker nifedipine and phospholipase C inhibitor U73122 inhibited NO formation and thus implicated participation of a second messenger pathway. Finally, in isolated rat gracilis vessels, rauwolscine completely inhibited the L-arginine-initiated vessel relaxation. Taken together, these data provide evidence for binding of arginine to membrane receptor(s), leading to the activation of endothelial NO synthase (eNOS) NO production through a second messenger pathway. These findings provide a previously unrecognized mechanistic explanation for the beneficial effects of L-arginine in the cardiovascular system and thus provide new potential avenues for therapeutic development.
authors.affiliation: Department of Surgery, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA. mjoshi20@yahoo.com
authors.forename: Mahesh S
authors.initials: MS
authors.lastname: Joshi
authors.forename: T Bruce
authors.initials: TB
authors.lastname: Ferguson
authors.forename: Fruzsina K
authors.initials: FK
authors.lastname: Johnson
authors.forename: Robert A
authors.initials: RA
authors.lastname: Johnson
authors.forename: Sampath
authors.initials: S
authors.lastname: Parthasarathy
authors.forename: Jack R
authors.initials: JR
authors.lastname: Lancaster
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000376:Agmatine / Q000737:chemistry / Q000494:pharmacology; D000814:Aniline Compounds; D001120:Arginine / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis; D002121:Calcium Channel Blockers / Q000494:pharmacology; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D020927:Dexmedetomidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D004789:Enzyme Activation / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D005456:Fluorescent Dyes; D006801:Humans; D019329:Idazoxan / Q000737:chemistry / Q000494:pharmacology; D048288:Imidazolines / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D015394:Molecular Structure; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D009566:Nitrates / Q000032:analysis; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D009573:Nitrites / Q000032:analysis; D011760:Pyrrolidinones / Q000494:pharmacology; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D015290:Second Messenger Systems / Q000502:physiology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014471:Umbilical Veins / Q000166:cytology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014966:Xanthenes; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D000814:Aniline Compounds; D002121:Calcium Channel Blockers; D016895:Culture Media, Serum-Free; D004963:Estrenes; C409648:Fluo 4; D005456:Fluorescent Dyes; D048288:Imidazolines; D008070:Lipopolysaccharides; D009566:Nitrates; D009573:Nitrites; D011760:Pyrrolidinones; D018341:Receptors, Adrenergic, alpha-2; D010566:Virulence Factors, Bordetella; D014966:Xanthenes; C084764:pertussis endotoxin; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015016:Yohimbine; D009569:Nitric Oxide; D020927:Dexmedetomidine; D000376:Agmatine; D001120:Arginine; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D010738:Type C Phospholipases; D009543:Nifedipine; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester; D019329:Idazoxan