E. Carmeli, M. Moas, S. Lennonc, and S.K. Powers (Israel)
matrix metalloproteinases; skeletal muscle; exercise
Metalloproteinases (MMPs) are a proteolytic enzymes that function in the extracellular matrix to degrade connective tissues yet, the relationship between exercise intensity and expression of MMP in muscles is unknown. Female rats (4 months old) completed two weeks of treadmill running at either low (18 m/min; ~50% VO2 max) and high intensity (32 m/min; ~70%VO2 max) speeds (up to 50 min/day). Non-running, sedentary animals served as controls. Muscle mRNA and protein levels of matrix metalloproteinases (MMP-2 and MMP-9) were assessed in gastrocnemius (Gast), Quadriceps, and Soleus (Sol) muscles by reverse transcriptase-polymerase chain reaction and western blotting, respectively. Results indicate that exercise did not alter MMP-9 in any skeletal muscle. Further, our data reveal that low intensity exercise did not alter the expression of MMP-2 in any of the muscles investigated. In contrast, high intensity exercise increased both mRNA and protein levels of MMP-2 in skeletal muscles containing a high percentage of fast type II fibers (i.e., Gast and superficial quadriceps). These results support the hypothesis that high intensity exercise is required to promote the expression of MMP-2 in skeletal muscles and that the influence of exercise on MMP-2 expression is dominant in muscles containing a high percentage of fast fibers.
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