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EXERCISE AND RESPIRATORY PHYSIOLOGY

Exercise promotes 7 integrin gene transcription and protection of skeletal muscle

¹Department of Kinesiology and Community Health, ²Beckman Institute for Advanced Science and Technology, and ³Department of Cell and Developmental Biology, University of Illinois, Urbana, Illinois; ⁴Department of Pharmacology, University of Nevada, Reno, Nevada

Submitted 7 February 2008 ; accepted in final form 1 September 2008

The 7β1 integrin is increased in skeletal muscle in response to injury-producing exercise, and transgenic overexpression of this integrin in mice protects against exercise-induced muscle damage. The present study investigates whether the increase in the 7β1 integrin observed in wild-type mice in response to exercise is due to transcriptional regulation and examines whether mobilization of the integrin at the myotendinous junction (MTJ) is a key determinant in its protection against damage. A single bout of downhill running exercise selectively increased transcription of the 7 integrin gene in 5-wk-old wild-type mice 3 h postexercise, and an increased 7 chain was detected in muscle sarcolemma adjacent to tendinous tissue immediately following exercise. The 7B, but not 7A isoform, was found concentrated and colocalized with tenascin-C in muscle fibers lining the MTJ. To further validate the importance of the integrin in the protection against muscle damage following exercise, muscle injury was quantified in 7^–/– mice. Muscle damage was extensive in 7^–/– mice in response to both a single and repeated bouts of exercise and was largely restricted to areas of high MTJ concentration and high mechanical force near the Achilles tendon. These results suggest that exercise-induced muscle injury selectively increases transcription of the 7 integrin gene and promotes a rapid change in the 7β integrin at the MTJ. These combined molecular and cellular alterations are likely responsible for integrin-mediated attenuation of exercise-induced muscle damage.

exercise; injury; repeated bout effect; tenascin-C