ARTERIAL AND VENOUS PLASMA-CATECHOLAMINES DURING SUBMAXIMAL STEADY-STATE EXERCISE

Arterial and venous plasma catecholamine responses to 15 min of cyclin g at 60% of maximal oxygen uptake were examined 11 times during exerci se and recovery in nine young men. Intra-arterial blood pressure, hear t rate and oxygen uptake were recorded continuously. All variables inc reased significantly during the initial 4 min, after which oxygen upta ke, diastolic blood pressure and arterial plasma adrenaline showed no further increase. Heart rate and plasma noradrenaline, however, contin ued to increase, although significantly more slowly, and were closely correlated (r = 0.81, 95% CI 0.71-0.87), as were systolic blood pressu re and heart rate (r = 0.78, 95% CI 0.71-0.87). Venous plasma adrenali ne showed a steady increase during the whole exercise period and thus a different response pattern from arterial plasma adrenaline. In concl usion, arterial plasma catecholamines respond to steady-state exercise by a two-phase pattern paralleling the changes in arterial blood pres sure and heart rate. Venous sampling does not reveal this association.