Autonomic blockade and coronary catecholamines and cyclic AMP in exercising man

To assess in man the effects of autonomic blockade on the response of catecholamines in the coronary circulation to dynamic exercise, arterial and coronary sinus catecholamine concentrations were measured in six patients during supine cycling exercise, following atropine 1.8 mg and oxprenolol 0.2 mg/kg iv. Although arterial concentrations did not increase significantly, coronary sinus catecholamine concentrations increased from 2.54 +/- 0.59 nmol/1 at rest 4.44 +/- 1.3 nmol/1 during exercise (P less than 0.05; one-tailed test) and were associated with a small increase in heart rate and coronary sinus cyclic AMP concentrations from 9.4 +/- 0.7 nmol/1 (rest) to 11.6 +/- 1.1 nmol/1 (exercise) (0.05 greater than P greater than 0.01). Although autonomic blockade may have increased catecholamine release, this was not reflected in an increased efflux of catecholamines from the heart, because similar increases in coronary sinus catecholamine concentrations occurred in the absence of autonomic blockade.