Aim: 

Muscle unloading induces numerous adaptive alterations in skeletal muscle and causes atrophy, an event characterized by decrease in size and wasting of muscle tissue and changes in the protein pattern. To specifically analyze the effect of hindlimb unloading (HU) on membrane proteins we used a proteomic approach based on the 2D-gel electrophoresis BN/SDS-PAGE.

Methods: 

Membrane vesicles from Soleus of control and HU rats and mice were purified using a multi-step centrifugation procedure and membrane proteins extracted with 1% Triton X-100. After electrophoresis, 2D-gels were silver stained.

Results: 

In rats, the comparison of 2D maps of HS vs controls revealed that approximately 30 proteins were significantly up-regulated and 12 down-regulated after suspension. In contrast, in mice few significant alterations in the Soleus protein pattern were found after HU. Furthermore, comparison of 2D maps between control rat and mouse Soleus shows different pattern of membrane proteins. Immunofluorescence studies confirm these differences between mouse and rat Soleus at rest. In particular, the expression level of myosins and AQP4 were different. Moreover, after HU in the mouse, AQP4, slow and fast myosins were not appreciably

altered, whereas in rats there was a remarkable increase of myosin IIA and AQP4 expression.

Conclusion: 

Results obtained indicate that microgravity causes alterations in the membrane protein pattern strong in rat and bland in mouse Soleus. The adaptation of murine skeletal muscle to HU may differ fairly from the adaptations typically seen in rat and human indicating the necessity to further evaluate the choice of the animal model for ground based hypogravity studies.