Department of Sport and Exercise Science, University of Auckland, New Zealand.
Acta Physiol (Oxf). 2012 Mar;204(3):393-402. doi: 10.1111/j.1748-1716.2011.02350.x. Epub 2011 Oct 17.
To determine whether voluntary free wheel (FW) or resistance wheel (RW) exercise or reduced muscle activity would influence maturational increases in muscle mass and the number of satellite cells (SCs) and myonuclei (MN) accrued by adulthood.
Hind limb muscles of male rats housed with, or without, FWs from 4 to 5, 7 or 10 weeks of age, and rats housed with RWs from 4 to 10 week of age, were evaluated. To assess the effect of reduced muscle activity, gastrocnemius muscles of 4-week-old rats were injected with botulinum toxin (Btx) and collected at 7 weeks of age. Muscle fibre size and the frequency of Pax7-positive SCs and MN were determined in 7- and 10-week-old muscles via immunohistochemical methods.
Free wheel exercise enhanced muscle growth and the frequency of SCs in the medial gastrocnemius (MG) (threefold) and vastus lateralis (VL) (twofold) of rats at 10 week of age. Resistance wheel exercise increased the number of SCs and MN (22-30%), with more muscle fibre nuclei being associated with larger fibre size, in the soleus, MG and VL muscles. Btx impaired the normal increases in muscle fibre size and the accrual of MN but not SCs.
A greater volume of exercise during maturational growth was important for enhancing SC numbers, whereas their conversion to MN required higher-intensity exercise. The enhanced muscle fibre nuclear populations may influence the capacity of the muscle to adapt to exercise, injury or disuse in later adulthood.
确定自愿自由轮（FW）或阻力轮（RW）运动或减少肌肉活动是否会影响肌肉质量和卫星细胞（SCs）和肌核（MN）数量的成熟增加，直至成年。
从 4 至 5、7 或 10 周龄开始，评估雄性大鼠后肢肌肉是否有 FW 或无 FW，以及从 4 至 10 周龄开始有 RW 的大鼠后肢肌肉。为了评估肌肉活动减少的影响，4 周龄大鼠的腓肠肌注射肉毒杆菌毒素（Btx），并在 7 周龄时收集。通过免疫组织化学方法确定 7 至 10 周龄肌肉中的纤维大小以及 Pax7 阳性 SCs 和 MN 的频率。
FW 运动增强了 10 周龄大鼠内侧腓肠肌（MG）（三倍）和外侧比目鱼肌（VL）（两倍）的肌肉生长和 SC 频率。RW 运动增加了 SCs 和 MN（22-30%）的数量，与更大的纤维大小相关的更多肌纤维核存在于比目鱼肌、MG 和 VL 肌肉中。Btx 损害了肌肉纤维大小和 MN 增加的正常情况，但不损害 SCs。
成熟生长期间更多的运动量对于增加 SC 数量很重要，而它们向 MN 的转化则需要更高强度的运动。增强的肌纤维核群体可能会影响肌肉在成年后期适应运动、损伤或失用的能力。
