Exercise training produces changes in free and conjugated catecholamines

In dogs the concentrations of conjugated dopamine in plasma have previously been shown to increase after exercise training. This study was done to determine whether conjugated norepinephrine and epinephrine also increase. Fifteen dogs were randomly divided into training (N = 8) or sedentary (N = 7) groups. All dogs were exercised acutely for 5 min at 4 mph with a 12% grade, following a 3-min warm-up, before and after either a 12-wk training or a 12-wk sedentary period. Free and conjugated catecholamines were determined in blood drawn at rest and during acute exercise using high-performance liquid chromatography (HPLC) with electrochemical detection. Before training, free norepinephrine, epinephrine, dopamine, and conjugated norepinephrine increased in plasma during acute exercise. Following the 12-wk training period, there were significant increases in free and conjugated dopamine and in conjugated norepinephrine in plasma taken at rest. There were no such increases in resting catecholamines after a 12-wk sedentary period. After either training or sedentary periods, dogs responded to acute exercise with an increase in free norepinephrine and a decrease in conjugated norepinephrine. Thus, after training both conjugated norepinephrine and dopamine, but not conjugated epinephrine, increased in plasma. The data suggest that sulfation of catecholamines increases as a result of exercise training.