The uptake kinetics and metabolism of extraneuronal noradrenaline in guinea-pig trachea as studied with quantitative fluorescence microphotometry.
1 Extraneuronal uptake of noradrenaline and alpha-methylnoradrenaline into single cells of guinea-pig tracheal smooth muscle have been studied by means of quantitative fluorescence microphotometry. 2 Fluorescence brightness due to accumulation of alpha-methylnoradrenaline was dose-dependent and was increased by the catechol-O-methyltransferase inhibitor drugs, tropolone or beta-thujaplicin (200 micrometer) but not by 3,4-dimethoxy-5-hydroxybenzoic acid (200 microgram). 3 Fluorescence brightness due to accumulation of noradrenaline was increased if animals were pretreated with the monoamine oxidase inhibitor drug, nialamide. 4 The study suggests that metabolism of amines by catechol-O-methyltransferase and monoamine oxidase can occur subsequent to extraneuronal uptake is guinea-pig tracheal smooth muscle. 5 The uptake of noradrenaline into tracheal smooth muscle was concentration-dependent, saturable, and had a Km of 156 micrometer.
D000818:Animals; D065098:Catechol O-Methyltransferase Inhibitors; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008856:Microscopy, Fluorescence / Q000379:methods; D009130:Muscle, Smooth / Q000378:metabolism; D009526:Nialamide / Q000494:pharmacology; D008771:Nordefrin / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D010783:Photometry / Q000379:methods; D014132:Trachea / Q000187:drug effects / Q000378:metabolism*
D065098:Catechol O-Methyltransferase Inhibitors; D008771:Nordefrin; D009526:Nialamide; D009638:Norepinephrine