Exercise-induced elevation of HSP70 is intensity dependent

TLDR

Exercise induces expression of the protective heat shock protein HSP70 in striated muscle. The study aimed to characterize how HSP70 induction relates to exercise intensity across muscles with different recruitment patterns in male Sprague‑Dawley rats. After a 60‑minute treadmill run, hearts, red and white vastus, and soleus muscles were harvested 24 h later and assayed for relative and absolute HSP70 content. HSP70 rose in heart and red vastus at speeds ≥24 m/min, in white vastus only above 27 m/min, and in soleus initially but then declined at the highest speeds, indicating that intensity‑dependent loading drives HSP70 expression.

Abstract

Exercise induces expression of the protective heat shock protein, HSP70, in striated muscle. To characterize the relationship between induction of this protein and exercise intensity in muscles exhibiting different recruitment patterns, male Sprague-Dawley rats were assigned to a sedentary control or one of seven exercise groups for which treadmill running speed varied between 15 and 33 m/min ( n = 8/group). Twenty-four hours after a single 60-min exercise bout, hearts, red and white portions of the vastus (RV and WV, respectively) muscles, and soleus (Sol) muscles were harvested and analyzed for both relative and absolute HSP70 content. Cardiac HSP70 was significantly elevated only when animals were exercised at 24 m/min and beyond. Similarly, HSP70 was elevated in RV at running speeds above 24 m/min but did not increase in WV until 27 m/min. In contrast, HSP70 content was initially elevated in the Sol but subsequently declined at the highest running speeds. The observed patterns of HSP70 expression in skeletal muscle were in general accordance with known muscle recruitment patterns and suggest that alterations in muscle loading, resulting from changes in exercise intensity, are an important component of exercise-induced increases in HSP70 content.