title: Acetylcholine and choline effects on erythrocyte nitrite and nitrate levels.
abstract: Acetylcholine has been detected in human blood. Acetylcholine receptors and acetylcholinesterase are present in erythrocyte membranes. We tested the acetylcholine and choline effects on nitric oxide metabolites (NOx), namely nitrites and nitrates, and observed if they are dependent on interactions with muscarinic receptors and acetylcholinesterase. Human erythrocyte suspensions were incubated with acetylcholine and choline in the absence or presence of 10 microM atropine or 10 microM velnacrine maleate. The nitrite and nitrate concentrations were determined by the Griess method. Acetylcholine or choline increased NOx control concentrations (P <0.001). The nitrite concentrations decreased in the presence of atropine or velnacrine maleate (P <0.03). The nitrate concentrations only decreased when velnacrine maleate was incubated with acetylcholine or choline (10 microM, P <0.03). These results demonstrated that acetylcholine and choline modulate nitric oxide metabolites on erythrocytes and this effect is mediated by interactions with erythrocyte membrane muscarinic receptors and membrane enzyme acetylcholinesterase. A hypothesis for the signal transduction mechanism has been discussed for acetylcholinesterase and muscarinic receptor (M1) participation.
authors.affiliation: Instituto de Bioquímica, Faculdade de Medicina de Lisboa, Unidade de Biopatologia Vascular, Instituto de Medicina Molecular, 1649-028 Lisboa, Portugal. mena_ist@hotmail.com
authors.forename: Filomena A
authors.initials: FA
authors.lastname: Carvalho
authors.forename: Rui
authors.initials: R
authors.lastname: Mesquita
authors.forename: João
authors.initials: J
authors.lastname: Martins-Silva
authors.forename: Carlota
authors.initials: C
authors.lastname: Saldanha
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000110:Acetylcholinesterase / Q000494:pharmacology; D000328:Adult; D018929:Cell Culture Techniques; D002794:Choline / Q000494:pharmacology*; D004912:Erythrocytes / Q000737:chemistry; D006801:Humans; D008297:Male; D009566:Nitrates / Q000097:blood*; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000097:blood*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction
chemical_list: D009566:Nitrates; D009573:Nitrites; D011976:Receptors, Muscarinic; D009569:Nitric Oxide; D000110:Acetylcholinesterase; D002794:Choline; D000109:Acetylcholine