The role of Heat Shock Proteins in cytoprotection of skeletal muscle

The aim of this study was to examine the Heat Shock Protein (HSP) response to a repeated bout of unaccustomed eccentric exercise. 9 volunteers (mean age 25 yrs.) performed 2 bouts of 70 maximal eccentric actions of the biceps, with 3 weeks between the bouts. Muscle biopsy tissue was homogenized and fractionated subcellulary for HSP analysis. Immediately after both bouts, muscle force was ~50% lower than pre‐exercise, and a translocation of small HSPs (sHSPs) from the cytosolic to the cytoskeletal fraction was observed. Compared to Bout‐1, however, muscle function recovered faster (p<0.05), sHSP accumulation in the cytoskeletal fraction was higher (p= 0.1), and cytosolic sHSP content was greater after Bout‐2 (p<0.05). Furthermore, an increase in HSP70 in the cytoskeletal (p<0.05) and cytosolic fractions (n.s.) was observed only after Bout‐2. In conclusion, total HSP content was elevated and the accumulation in the cytoskeletal fraction was more pronounced after Bout‐2, indicating a role for HSPs in the repeated bout effect, most likely by protecting muscle cells from stress‐induced alterations in protein structure and function. This may result in improved recovery of cellular homeostasis following repeated exercise. The study was supported by the Norwegian School of Sports Sciences.