RESUMO
The role of exercise in skeletal muscle hypertrophy was examined using op/op mice, which have a hereditary deficiency in the differentiation of macrophages. A tenotomy was performed to produce a compensation load for the soleus and plantaris muscles in op/op mice and a control group. After one week, the weight of the soleus and plantaris muscles had increased significantly. The cross-sectional area of the muscle fiber in the soleus of the control group increased as a result of the compensation load, indicating that the tenotomy had induced muscle fiber hypertrophy. However, the cross-sectional area of the muscle fiber in the soleus of the op/op mouse group did not change significantly. Instead, the tenotomy induced an increase in the number of thin fibers. The cross-sectional area of muscle fibers in the plantaris muscle, which is a fast muscle, decreased in the op/op mouse group. In conclusion, compensation loads in macrophage-deficient op/op mice do not result in muscle fiber hypertrophy.