EFFECT OF BETA-ADRENOCEPTOR STIMULATION ON OXYGEN-CONSUMPTION AND TRIGLYCERIDE FATTY-ACID CYCLING AFTER EXERCISE

The purpose of this study was to characterize the effects of prolonged beta-adrenoceptor stimulation on O-2 uptake and triglyceride/fatty ac id (TG/FA) cycling during rest with and without previous exercise. Eig ht men performed two exercise (90 min cycling at 56 +/- 3 (SD)% of max imal O-2 uptake, followed by 4.5 h bed rest) and two rest-control expe riments. In one rest and one exercise experiment a bolus dose (5 mu g) of the beta-adrenoceptor agonist isoprenaline was given immediately a fter exercise. followed by a continuous infusion (20 ng kg(-1) min(-1) ), and at the corresponding time in the rest experiment. In the other experiments saline was given instead. The O-2 uptake increased in the postexercise period both with and without beta-stimulation. The total excess post-exercise oxygen consumption (EPOC) was not different betwe en saline (8.1 +/- 1.8 (SE) L) and isoprenaline administration (10.8 /- 1.8 L, P = 0.40). Also, the total accumulated increase in O-2 uptak e for the 4.5 h period after isoprenaline infusion was not different b etween the rest (12.5 +/- 2.0 L) and the exercise experiments (15.2 +/ - 1.7 L, P = 0.40). The rate of TG/FA cycling increased after both exe rcise and isoprenaline treatment, but no interaction effect was found. in conclusion, the increases observed in O-2 uptake and the rate of T G/FA cycling during beta-adrenoceptor stimulation were not increased b y a previous exercise bout.