Role of Beta-Adrenergic Mechanisms in Exercise Training-Induced Metabolic Changes in Respiratory and Locomotor Muscle

Abstract

To test the hypothesis that β-adrenergic stimulation is required for the normal increase in oxidative capacity of respiratory and locomotor skeletal muscle in response to exercise training, we examined the effects of (3-blockade on muscle oxidative capacity in trained and sedentary rats. Thirty-four female adult Sprague-Dawley rats were randomly divided into four experimental groups: 1) trained + propranolol (TP); 2) trained + sham injection (TS); 3) sedentary + propranolol (SP); and 4) sedentary + sham injection (SS). Training increased (p<0.05) citrate synthase (CS) activity in the plantaris (+29 %) and costal diaphragm (+ 12 %) of TS animals compared to SS animals. In contrast, training did not (p>0.05) increase costal diaphragm CS activity in TP animals compared to the SS group. Further, although training increased (p<0.05) plantaris CS activity in the TP group (+ 18 %) compared to the SP group, the training-induced increase in muscle CS activity was 11 % lower (p<0.05) than observed in TS animals. Collectively, these results suggest that (β-adrenergic mechanisms may play a role in the normal training-induced increase in oxidative capacity in both respiratory and locomotor skeletal muscles.

Key words

Propranolol - adrenergic stimulation - catecholamines - mitochondria - diaphragm - plantaris