title: The role of monoamine oxidase in the metabolism of exogenous noradrenaline by the human saphenous vein.
abstract: Human saphenous vein segments were obtained from patients subjected to coronary bypass surgery. As determined by HPLC-ED, the veins had a relatively low content of noradrenaline and high content of the deaminated metabolites, dihydroxyphenylglycol (DOPEG) and dihydroxymandelic acid (DOMA). In vein segments which had been incubated with 3H-noradrenaline (0.1 mumol/l), the oxidative deamination pathway predominated over the O-methylating one. Deamination occurred both at the neuronal and extraneuronal level; DOPEG appearing to be a good index of intraneuronal deamination, whereas DOMA and O-methylated and deaminated metabolites were mainly formed extraneuronally. Both MAO type A and MAO type B selective inhibitors reduced the deamination of noradrenaline; deamination was also found to be partially sensitive to semicarbazide. Inhibition of neuronal uptake or of deamination increased O-methylation. The human saphenous vein thus metabolizes exogenous noradrenaline following a pattern which substantially differs from that shown to occur in various blood vessels from other animal species.
authors.affiliation: Laboratório de Farmacologia, Faculdade de Medicina, Porto, Portugal.
authors.forename: D
authors.initials: D
authors.lastname: Branco
authors.forename: M
authors.initials: M
authors.lastname: Caramona
authors.forename: D
authors.initials: D
authors.lastname: Araújo
authors.forename: W
authors.initials: W
authors.lastname: Osswald
mesh_terms: D003641:Deamination; D004298:Dopamine / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008995:Monoamine Oxidase / Q000378:metabolism / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism*; D012501:Saphenous Vein / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*
chemical_list: D008995:Monoamine Oxidase; D004298:Dopamine; D009638:Norepinephrine