Journal of Applied Physiology, Vol 68, Issue 2 452-456, Copyright © 1990 by American Physiological Society
Plasma free and sulfoconjugated catecholamines during sustained exercise
M. S. Sothmann, J. Blaney, T. Woulfe, S. Donahue-Fuhrman, K. Lefever, A. B. Gustafson and V. S. Murthy
Department of Human Kinetics, School of Allied Health Professions, University of Wisconsin-Milwaukee.
Previous research established a relationship between circulating
sulfoconjugated norepinephrine (NE-SO4) and oxygen consumption at various
exercise intensities. In this study, the stability of the NE-SO4 response
was examined during sustained exercise at a constant relative intensity.
Seven trained men bicycled at 78 +/- 3% of their maximal O2 consumption for
28 min and then rested on the ergometer for a comparable duration. After a
30-min rest, plasma samples were collected through an indwelling catheter
at 7-min intervals during the exercise and recovery periods. Free NE and
epinephrine increased sixfold during exercise. These changes were
accompanied by increases in sulfoconjugated catecholamines, but only NE-SO4
achieved statistical significance (rest, 712 +/- 602; exercise, 1,329 +/-
1,163 pg/ml). This occurred at three collection periods (14, 21, and 28
min). Approximately 35, 52, and 95% of NE, epinephrine, and dopamine,
respectively, existed as sulfoconjugated during exercise. Subject variation
was present in the sulfoconjugated catecholamine response that could not be
attributed to corresponding differences in circulating free catecholamine
release. These findings implicate blood flow as a factor in the
sulfoconjugation of NE, but not epinephrine or dopamine.
