Disruption of cellular constituents including inhibition or "downregulation" of metabolic enzyme activity has been associated with free radical stress in locomotor muscle with acute, strenuous exercise. However, the effects of acute, strenous exercise on important metabolic and antioxidant enzyme activity levels in the diaphragm are unknown. Twenty 4-month-old and twenty 24-month-old female Fischer-344 rats were divided at random into young exercised (YE; n = 10)/old exercised OE; n = 10); young control (if YC; n = 10)/old control (OC; n = 10) groups. Animals in both young and old exercise groups ran on a treadmill (10% uphill grade) for 40 min at ∼ 75% of age group VO2max. Immediately following the treadmill run, both exercise and control groups were euthanized with sodium pentobarbital. Costal (COD) and crural diaphragm (CRD) were quickly removed and frozen in liquid nitrogen. Lipid peroxidation was significantly increased (P < 0.05) in COD of YE vs. YC rats. Activity of the antioxidant enzyme glutathione peroxidase (GPX) was unaltered in the diaphragm by acute exercise (P > 0.05) in both age groups. There was a significant increase in superoxide dismutase (SOD) activity with exercise (P < 0.05). POst-hocs revealed SOD activity was ∼ 20% greater (P = 0.066) in YE CRD only. Activities of the metabolic enzymes phosphofructokinase (PFK), succinate dehydrogenase (SDH), and citrate synthase (CS) were not affected by acute exercise in YE or OE. Strenuous exercise resulted in a small trend towards a decrease in 3-hydroxyacyl-CoA dehydrogenase (HADH) activity in YE COD (P = 0.115) and YE CRD (P = 0.082). We conclude that the employed bout of exercise induces some free radical stress, while metabolic enzymes are protected, in the diaphragm.
Bibliographical noteFunding Information:
The authors would like to thank Drs. J. Richard Coast, Michael Pollock, Diane Spitler, and Wendell Stainsby for their valuable input in preparation of this manuscript. This research was funded in part by the American Lung Association (FL affiliate).
Copyright 2014 Elsevier B.V., All rights reserved.
- Enzyme, metabolic
- Mammals, rats
- Muscle, diaphragm
- Oxygen radicals