Abstract: Objective To investigate the DNA methylation of skeletal muscle in spastic paralysis rats and correlation with the muscle fiber configuration. Methods 100 5-day old Wistar rats were randomly divided into model group and control group. The former was established the spastic paralysis modle and reared for 30 days. Then, tissues from the gastrocnemius of all the rats were observed with triplicate DNA methylation, myosin heavy chain-I (MHC-I) mRNA with RT-PCR and transmission electron microscopy. Results The DNA methylation was (4.95±0.83)×10% in the model group, significantly less than (6.59±0.75)×10% in the control group (P<0.001); while the MHC-I mRNA was (1.23±0.31), significantly more than (0.44±0.29) in the control group (P<0.001). The Z-line was disordered, and the mitochondria near the Z-line increased, with edema and partially broken in cristae. The balance between the thick and thin filaments was broken, and myofibrils envelope fused. Conclusion Hypomethylation and hyperexpression of MHC-I mRNA have been found in skeletal muscle of spastic paralysis rats, which may result in type I fibers increase. However, there was no sufficient evidence to support the correlation between the DNA methylation and the secondary pathological changes.

Key words: spastic paralysis, methylation, ultrastructure, myosin heavy chain-I