Time course changes in AQP4 expression patterns in progressive skeletal muscle atrophy during the early stage of denervation.

OBJECTIVES: In the skeletal muscles, water metabolism is mainly regulated by water channel aquaporin 4 (AQP4). Although the expression level of AQP4 was reduced by long-term denervation, during denervation the relationship between muscle atrophy initiation and AQP4 expression decrease initiation remains unknown. The present study examined the relationship between the timing of muscle atrophy initiation and that of AQP4 expression decrease initiation, during the early stage of denervation. METHODS: Female 344 rats (8 weeks of age) were randomly assigned to control (C), day 1 post-sciatic denervation (D1), day 4 post- sciatic denervation (D4) and day 7 post- sciatic denervation (D7) groups (n=6 per group). In the tibialis anterior (TA) muscles of each group, the expression levels of some target proteins were quantified by Western blot analysis. RESULTS: The expression level of AQP4 significantly decreased on day 4 post-denervation (p<0.05). Moreover, the beginning of the decrease in AQP4 expression level was concurrent with the timing of muscle atrophy in the skeletal muscles during the early stage of denervation. CONCLUSIONS: The present study suggested that the progression of the decrease in the AQP4 expression level is partly related to the progression of muscle atrophy during the early stage of denervation.