Study of diurnal fluctuations of plasma methoxyamines in healthy volunteers.
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.
Hoizey
Guillaume
G
Service d'Endocrinologie, Hôpital Robert Debré, CHU de Reims, France. ghoizey@aol.com
Lukas-Croisier
Céline
C
Frances
Carole
C
Grulet
Hervé
H
Delemer
Brigitte
B
Millart
Hervé
H
Devillier
Philippe
P
Caron
Jean
J
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
D002395:Catecholamines; D009647:Normetanephrine; D008676:Metanephrine; D009638:Norepinephrine; D004837:Epinephrine