Lipid Peroxidation and Protein Turnover after Trauma and Cold Treatment in Skeletal Muscle of Exercise-trained Rats

Abstract

Objective: To examine the effects of muscle trauma and cold application on indicators of oxygen free radical (OFR) and protein levels in exercise trained rat skeletal muscle. Design: Randomized intervention study following an exercise training program. Skeletal muscle tissue analysis 72 hours after trauma and cold treatments. Setting: University animal research laboratory. Subjects: 70 female Sprague-Dawley rats weighing 200-250 grams, housed in wire cages, provided with rat food and water ad libitum. Interventions: 35 rats took part in a daily running program for 8 weeks. After the training program, 28 rats were randomly assigned to one of four groups to study indices of OFR levels after trauma and cold treatments. Further, 28 rats were randomly assigned to one of four groups to study muscle protein content after trauma and cold treatment. A sedentary group (N=7) was included in each analysis as a control group. Groups that received trauma were subjected to a single impact blunt trauma to the medial aspect of the gastrocnemius muscle of the left leg. Following the trauma procedure, groups that received cold treatment had 6 cold applications for 10 minutes, twice per day over a 72 hour period with a 3 × 2 inch gel cold pack, stored at -4°C. Main outcome measures: Medial gastrocnemius muscles were analyzed at 72 hours post-trauma for citrate synthase, indicators of OFR (malonaldehyde and lipofuscin) and protein content. Results: After the endurance training program, significant increases (p<0.05) in citrate synthase activity and protein levels were elicited, but the indices of lipid peroxidation (OFR indicators) were unaltered when compared to sedentary and exercise groups. Following trauma, the net loss of pre-existing protein was statistically significant (p<0.05) and lipid peroxidation activity increased slightly, but not significantly. Further, modulations in lipid peroxidation and protein content were induced in muscle by cold treatment followed by trauma (p<0.05) as the application of cold prevented or delayed indicators of OFR activity and protein loss in the medial gastrocnemius muscle. Conclusions: Cold treatment applied to traumatized muscle significantly decreased lipofuscin content (indices of OFR) and offset the catabolic response in protein content during the inflammatory phase. The early application of cold immediately after trauma is recommended within the protocol guidelines.