MUSCLE INFLAMMATORY CELL CONCERNTRATIONS FOLLOWING DOWN-HILL RUNNING

The purpose of the study was to examine the kinetics of muscle inflammatory cell concentrations in rat solei following eccentric exercise. Male Wistar rats performed either down-hill running (n = 35; 17m/min,-16% grade) or normal cage activity (controls; n = 5). Solei were obtained at the following post-exercise time points: 0 (n = 6), 2(n = 6), 6(n = 5), 24(n = 6), 48(n = 6), and 72h(n = 6). Down-hill running induced muscle injury as indicated by a significant increase (P ≥ 0.05) in blood creatine kinase activity and histological signs of injury in hematoxylin and eosin stained cross sections. Macrophage subpopulations (ED1+ and ED2+) were determined using immunohistochemistry. ED1+ macrophage concentrations were significantly higher at 24h relative to controls. The percentage of myofibers invaded by ED1+ macrophages, an indicator of necrosis, was also significantly higher at 24h relative to controls. ED2+ macrophage concentrations were not significantly elevated at any post-exercise time-point. The results suggest that down-hill running causes an elevation in muscle ED1+ macrophage concentrations but does not influence the concentrations of ED2+ macrophages.