C. Caillaud et al., Antioxidants and mitochondrial respiration in lung, diaphragm, and locomotor muscles: Effect of exercise, FREE RAD B, 26(9-10), 1999, pp. 1292-1299
Previous studies have shown that exhaustive exercise may increase reactive
oxygen species (ROS) generation in oxidative muscles that may in turn impai
r mitochondrial respiration. Locomotor muscles have been extensively examin
ed, but there is few report about diaphragm or lung. The later is a privile
ged site for oxygen transit. To compare the antioxidant defense system and
mitochondrial function in lung, diaphragm and locomotor muscles after exerc
ise, 24 young adult male rats were randomly assigned to a control (C) or ex
ercise (E) group. E group rats performed an exhaustive running test on a mo
torized treadmill at 80-85% (V)over dot O-2max. Mean exercise duration was
66 +/- 2.7 min. Lung, costal diaphragm, mixed gastrocnemius, and oxidative
muscles (red gastrocnemius and soleus: RG/SOL homogenate) were sampled. Mit
ochondrial respiration was assessed in tissue homogenates by respiratory co
ntrol index (RCI: rate of uncoupled respiration/rate of basal respiration)
measurement. Lipid peroxidation was evaluated by malondialdehyde concentrat
ion (MDA) and we determined the activity of two antioxidant enzymes: supero
xide dismutase (SOD) and glutathione peroxidase (GPX). We found elevated ba
sal (C group data) SOD and GPX activities in both lung and diaphragm compar
ed to locomotor muscles (p < .001). Exercise led to a rise in GPX activity
in red locomotor muscles homogenate (GR/SOL; C = 10.3 +/- 0.29 and E = 14.4
+/- 1.51 mu mol.min(-1).gww(-1); p < .05), whereas then was no significant
change in lung and diaphragm. MDA concentration and mitochondrial RCI valu
es were not significantly changed after exercise. We conclude that lung and
diaphragm had higher antioxidant protection than locomotor muscles. The ex
ercise test did not lead to significant oxidative stress or alteration in m
itochondrial respiration, suggesting that antioxidant function was adequate
in both lung and diaphragm in the experimental condition. (C) 1999 Elsevie
r Science Inc.