Figure 2. IL-8 immunohistochemical expression in skeletal muscle tissue before and after 3 h of bicycle exercise.

A, before the exercise began, IL-8 expression was almost absent in the muscle tissue. B, By 3 h, when the exercise had just ended, the muscle tissue showed a comparable IL-8 expression relative to the level seen before exercise. C, by 4.5 h after exercise, the IL-8 expression was significantly increased in the skeletal muscle tissue, which showed a high level of IL-8 both in general in the cytoplasm and related to the cell membranes, as well as in vessels in the muscle. D, ATPase-stained section. This is the neighbouring section to that seen in C. By comparing C and D, it is seen that both muscle fibre types express IL-8 after exercise. E and F, IL-8 expression was still very high, and peaked at 6 (E) and 9 h (F) following the bicycle exercise. G, after 24 h, the levels of IL-8 protein had decreased again, and the staining appeared homogeneous and mildly increased in the fibres. H and I, higher magnification of skeletal muscle tissue at 9 h following exercise. As shown, IL-8 protein is mainly expressed in the cytoplasm, and it is also expressed in the membranes, including the nuclei. We also detected intermittently vascular IL-8 expression in the vessel endothelium of the muscle tissue. Scale bars: A–G, 50 μm; H, 29 μm; I, 14 μm.