Plasma catecholamine responses to exercise after training with beta-adrenergic blockade

Abstract

Exercise training has been shown to decrease plasma norepinephrine (NE) and epinephrine (EPI) levels during absolute levels of submaximal exercise, which may reflect alterations in sympathetic tone as a result of training. To determine if beta-adrenergic blockade altered these changes in the plasma concentration of catecholamines with exercise conditioning, we studied the effects of beta-adrenergic blockade on NE and EPI at rest and during exercise in 24 healthy, male subjects after a 6-wk exercise training program. The subjects were randomized to placebo (P), atenolol 50 mg twice daily (A), and nadolol 40 mg twice daily (N). There were no changes in resting NE and EPI compared with pretraining values in any subject group. During the same absolute level of submaximal exercise NE decreased in P and A but was unchanged in N, whereas EPI decreased only in P. At maximal exercise all three groups developed significant increases in NE after training that paralleled increases in systolic blood pressure. EPI at maximal exercise increased after training with N but was unchanged with P or A. These training-induced changes in plasma catecholamine levels were masked or blunted when the A and N groups were studied while still on medication after training. Thus beta-adrenergic blockade has important effects on adaptations of the sympathetic nervous system to training, especially during submaximal exercise.

Effects of caffeine and promazine hydrochloride on plasma catecholamines in Thoroughbreds at rest and during treadmill exercise

“…Plasma CA levels may be useful for investigating the pharmacological effects of drugs at rest and during exercise (Dimsdale et al 1984;Collomp et al 1994;Graham and Spriet 1995;Jackman et al 1996), particularly in the assessment of drugs which have effects through actions on adrenoceptors (Dimsdale etal. 1984;Wolfel et al 1990). However, plasma CA levels have seldom been measured in pharmacological studies of the horse (Snow et al 1979).…”

Physiological factors that regulate the use of endogenous fat and carbohydrate fuels during endurance exercise

“…Both cross-sectional studies of trained and untrained subjects and longitudinal training studies have found that training either does not change or actually decreases the rate of appearance (Ra) of fatty acids into plasma during exercise performed at the same absolute intensity (Jansson & Kaijser, 1987;Martin et al 1993;Klein et al 1994;Horowitz & Klein, 2000a). Plasma catecholamine concentrations, which stimulate lipolysis of adipose tissue TG during exercise, are lower during exercise performed at the same absolute intensity before and after training (Wolfel et al 1990;Phillips et al 1996b;Friedlander et al 1998b) despite a training-induced increase in the capacity to secrete adrenaline (Kjaer & Galbo, 1988). In addition, training does not alter lipolytic sensitivity to adrenaline.…”