title: Study of diurnal fluctuations of plasma methoxyamines in healthy volunteers.
abstract: OBJECTIVE
  We studied the diurnal fluctuations of plasma concentrations of methoxyamines (metanephrine and normetanephrine) and of their parent amines (epinephrine and norepinephrine) in normotensive subjects.
  
  
  METHODS
  Serial blood sampling at 09.00 h, 11.00 h, 12.00 h, 14.00 h, 16.00 h, 18.00 h and 20.00 h in 28 healthy volunteers at rest. Determination of plasma concentrations of free catecholamines and total methoxyamines (free and sulpho-conjugates) was carried out by high-performance liquid chromatography with electrochemical detection.
  
  
  RESULTS
  Mean (+/- SD) plasma concentrations of total metanephrine (MN) and normetanephrine (NMN) were 4.31 +/- 1.73 nmol/l (range: 0.96-9.3 nmol/l) and 8.13 +/- 2.54 nmol/l (range: 3.14-17.0 nmol/l), respectively. The NMN/MN ratio ranged between 0.8 and 7.8 (mean +/- SD 2.1 +/- 1.0). Mean plasma concentrations of free epinephrine and norepinephrine were 0.21 +/- 0.12 nmol/l (range: 0.06-1.39 nmol/l) and 1.61 +/- 0.62 nmol/l (range: 0.47-4.01 nmol/l), respectively. Despite marked intraindividual fluctuations, mean methoxyamine and catecholamine levels remained constant over the entire duration of the experiment.
  
  
  CONCLUSIONS
  The absence of fluctuations of plasma levels of total methoxyamines suggests that their measurement could be carried out at any time within the diurnal time frame. Further investigations, however, remain necessary to validate these findings in patients with hypertension and/or pheochromocytoma, and to explain the ever important intraindividual variation in plasma concentrations of methoxyamines and of their parent compounds.
authors.affiliation: Service d'Endocrinologie, Hôpital Robert Debré, CHU de Reims, France. ghoizey@aol.com
authors.forename: Guillaume
authors.initials: G
authors.lastname: Hoizey
authors.forename: Céline
authors.initials: C
authors.lastname: Lukas-Croisier
authors.forename: Carole
authors.initials: C
authors.lastname: Frances
authors.forename: Hervé
authors.initials: H
authors.lastname: Grulet
authors.forename: Brigitte
authors.initials: B
authors.lastname: Delemer
authors.forename: Hervé
authors.initials: H
authors.lastname: Millart
authors.forename: Philippe
authors.initials: P
authors.lastname: Devillier
authors.forename: Jean
authors.initials: J
authors.lastname: Caron
mesh_terms: D000328:Adult; D002395:Catecholamines / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm; D004837:Epinephrine / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000097:blood; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D009647:Normetanephrine / Q000097:blood; D012016:Reference Values
chemical_list: D002395:Catecholamines; D009647:Normetanephrine; D008676:Metanephrine; D009638:Norepinephrine; D004837:Epinephrine