[Effects of tetramethylpyrazine on nitric oxide synthase activity and calcium ion concentration of skeletal muscle in hindlimb unloading rats].

Objective: To explore the effects of tetramethylpyrazine on the nitric oxide synthase activity and calcium ion concentration in skeletal muscle fiber and decipher the possible mechanisms of anti-muscle atrophy function of tetramethylpyrazine in hindlimb unloading rats.

Methods: Hindlimb unloading (HLU) rats were used as a muscle atrophy model to study the activity of nitric oxide synthase by colorimetry. The concentration of intracellular calcium ion was measured by laser scanning confocal microscope. A total of 18 female rats were randomly divided into 3 groups: control (CON), hindlimb unloading with water (HLU + W) and hindlimb unloading with tetramethylpyrazine (HLU + Tmp) (n = 6 each).

Results: (1) Compared with CON, the activity of nitric oxide synthase decreased by 28% in HLU + W (P < 0.05) and decreased by 46% in HLU + Tmp (P < 0.01). The activity of nitric oxide synthase less decreased in HLU + Tmp than that in HLU + W, but it was not statistically significant (P > 0.05). (2) Compared with CON, the concentrations of intracellular calcium ion in HLU + W and HLU + Tmp increased by 330% and 86% respectively (P < 0.01). Compared with HLU + W, the concentration of intracellular calcium ion decreased by 130% in HLU + Tmp (P < 0.01).

Conclusion: The activity of nitric oxide synthase decreases and the concentration of calcium ion increases in hindlimb unloading rats. And tetramethylpyrazine may suppress the calcium ion overloading but not the activity of NOS associated with disuse muscular atrophy.