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Plasma free and sulfoconjugated catecholamines during sustained exercise
M S Sothmann1, J Blaney, T Woulfe
1Department of Human Kinetics, School of Allied Health Professions, University of Wisconsin-Milwaukee.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1990
Summary
Sulfoconjugated norepinephrine (NE-SO4) levels significantly increase during sustained exercise, suggesting blood flow influences its formation. This response varied among individuals despite similar free catecholamine levels.
Area of Science:
- Exercise Physiology
- Biochemistry
- Human Physiology
Background:
- Previous studies linked circulating sulfoconjugated norepinephrine (NE-SO4) to oxygen consumption during exercise.
- The stability and response patterns of NE-SO4 during sustained, constant-intensity exercise were not well-established.
Purpose of the Study:
- To investigate the stability of the NE-SO4 response during prolonged, moderate-intensity exercise.
- To determine the proportion of sulfoconjugated catecholamines (norepinephrine, epinephrine, dopamine) during sustained exercise.
- To explore potential factors influencing individual variations in the NE-SO4 response.
Main Methods:
- Seven trained men performed 28 minutes of cycling at 78% of maximal oxygen consumption, followed by a rest period.
- Plasma samples were collected at 7-minute intervals during exercise and recovery using an indwelling catheter.
- Concentrations of free and sulfoconjugated norepinephrine, epinephrine, and dopamine were measured.
Main Results:
- Free norepinephrine and epinephrine increased sixfold during exercise.
- Sulfoconjugated norepinephrine (NE-SO4) showed a statistically significant increase during exercise (from 712 to 1,329 pg/ml).
- During exercise, approximately 35% of NE, 52% of epinephrine, and 95% of dopamine were sulfoconjugated, with significant individual variability in NE-SO4 response.
Conclusions:
- NE-SO4 levels are significantly elevated during sustained exercise at a constant relative intensity.
- Blood flow appears to be a key factor in the sulfoconjugation of norepinephrine, but not epinephrine or dopamine.
- Individual differences in NE-SO4 response during exercise warrant further investigation.