The effect of increased functional load on the activation of satellite cells in the skeletal muscle of adult rats.

The comparison of the number of satellite cells in the fast oxidative glycolytic muscle fibers of m. quadriceps femoris in males of normal Wistar rats aged 16-17 weeks (5 animals) and rats trained for endurance (5 animals) was made. After six weeks of treadmill running at a speed of 35 m/min in an increasing regimen, the number of satellite cells in trained animals (9.59 +/- 1.09%) increased over 2.5-fold in comparison to controls (3.41 +/- 0.26%) within 24 hours. At the ultrastructural level complete and focal injuries of some muscle fibers and the partial denervation of individual muscle fibers were recorded in trained rats. It was proposed that the focal functional denervation of muscle fibers could be one of the factors for the activation of satellite cells in endurance exercise. Some trained rats demonstrated small groups of extra- and perisynaptic satellite cells under the basal membrane of muscle fibres, partial detachment of satellite cells from the surface of muscle fiber and presence in the interstitial space cell containing filaments.