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Expression of cathepsins B, H, L, and S in soleus and gastrocnemius of hindlimb suspended rats

Abstract:

Muscle loss due to exposure to microgravity is a limiting factor to prolonged space travel. The goal of this study was to determine whether weightlessness alters the expressed activity of the lysosomal cysteine proteinases in skeletal muscle using the tail/hindlimb suspension model. Adult male and female Sprague-Dawley rats were treated for different periods of head-down tail suspension, nonsuspended controls were in cages of similar dimensions. Following suspension, rats exhibited muscular atrophy in the hindlimb skeletal muscles. The soleus and gastrocnemius of the rats were removed and sectioned into small pieces weighing ∼100 to 200 mg. The samples were homogenized, frozen, thawed, and centrituged. The levels of cathepsins B, H, L, and S were individually determined from the supernatant with the specific peptide fluorogenic substrates: Z-R-R-MCA for cathepsin B, R-MCA for cathepsin H, Z-F-R-MCA for cathepsin L, and Z-V-V-R-MCA for cathepsin S. The protein concentrations were determined by Lowry's method. We found these techniques to be very sensitive in determining expression of catheptic activity in skeletal muscle for the control nonsuspended rats and suspended rats. This study was supported by the Arkansas Space Grant Consortium.