CATECHOLAMINE METABOLIC PATHWAYS AND EXERCISE TRAINING - PLASMA AND URINE CATECHOLAMINES, METABOLIC ENZYMES, AND CHROMOGRANIN-A

Background. Because acute exercise increases systemic catecholamines, we sought to determine whether exercise training would alter daily or exercise-related catecholamine release and inactivation. Methods and Results. In 24-hour urine collections, catecholamines and metabolites provided indexes of overall oxidative deamination, sulfation, and O-methylation. Plasma catecholamines, the sulfoconjugates of each, and chromogranin-A were determined at rest and during exercise in 10 well-trained male subjects and nine minimally trained male subjects (maximal oxygen uptake 55.2 and 42.5 ml/kg/min, respectively), and levels of activities of catechol-O-methyltransferase (COMT), monamine oxidase B (MAO-B), and thermolabile phenolsulfotransferase (TL-PST) were also determined. Plasma-free catecholamines showed minimal differences between the two groups at submaximal exercise (4 minutes) but large differences at maximal exercise, reflecting the different exercise levels attained. Inactivation of plasma catecholamines by sulfation across rest and exercise tended to be greater in the well-trained group, with small increases in both plasma sulfoconjugated dopamine and sulfoconjugated norepinephrine. In the well-trained group, urinary metabolites demonstrated trends toward increased dopamine release (p < 0.07) and small increases in the daily release of epinephrine and its sulfoconjugated metabolities. Indexes of deamination, sulfoconjugation, and O-methylation, with the exception of a reduced deamination of dopamine and the activities of COMT, MAO-B, and TL-PST were not different in the two groups. Conclusions. Despite considerable differences in the exercise activities per week between well-trained and minimally trained individuals, there were minimal differences in the release and metabolism of catecholamines at rest or during exercise.