Blunted HSP70 Response to Acute Exercise in Well-Trained Skeletal Muscle

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2183 In response to exercise, human skeletal muscle can produce heat shock protein 70 HSP70) which may serve as an important mechanism for muscular adaptation. It is known that HSP70 can be induced in untrained muscle by a short exercise bout, and in well-trained muscle HSP70 response depends on exercise intensity. It seems that low intensity exercise does not augment HSP70 expression in well-trained muscle. PURPOSE: To investigate whether HSP70 reponse to acute exercise in well-trained human skeletal muscle is blunted. METHODS: Six male well-trained rowers (17.6 ± 0.3 yr, 86.7 ± 3.4 kg) underwent a short bout (1,5 h each) of high intensive (HIE) and low intensity endurance exercise (LIEE) on separate days. Muscle samples were obtained from musculus vastus lateralis before and at 1h and 6h after exercise bout. HSP70 at protein level was determined using Western blot (2,5μg total protein loaded), and HSP70 mRNA was estimated using quantitative real time RT-PCR. RESULTS: HSP70 did not change significantly after HIE (before: 47.1 ± 11.2 ng; 1h: 44.2 ± 9.6 ng; 6h: 46.2 ± 11.8 ng, respectively), this was also the case for LIEE (before: 54.0 ± 14.2 ng; 1h: 38.5 ± 9.5 ng; 6h: 53.3 ± 11.8 ng, respectively). Similar results were derived at mRNA level, expressed as HSP70/HPRT mRNA ratio (as house-keeping gene). CONCLUSION: It has been shown that a short bout of exercise induces HSP70 in untrained muscle. In contrast, no upregulation of HPS70 at both protein and mRNA level could be observed in muscle of well-trained rowers. These data support that HSP70 response to acute exercise in well-trained skeletal muscle is blunted. While HSP70 may serve as an indicator for cellular stress during physical training in untrained muscle, this could not be assumed for highly trained muscle.

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