Alteration in skeletal muscle antioxidant defense gene expression profile following multiple exposures to hyperthermia

Abstract

Heat load is a potent stressor, due in part, to alterations in the production of reactive oxygen species (ROS). The ability of skeletal muscle to mitigate potentially harmful effects of hyperthermia and elevated ROS is unclear. Study objectives were to determine the effects of single and multiple bouts of acute heat stress (HS) on the expression of genes associated with antioxidant defense in soleus (type I; oxidative) and tibialis anterior (TA; type II; glycolytic) skeletal muscles. Male Sprague Dawley rats (n = 12; 9 mo) were randomly assigned to one of 3 treatment groups; thermoneutral (TN; 22°C) or either 1 or 2 exposures to HS conditions (40°C, 20% relative humidity, 6 h each). Rats were anesthetized and skeletal muscles were collected. Total RNA was isolated and cDNA generated for a real‐time PCR‐based array (SABiosciences). During TN, gene expression of antioxidants (catalase, glutathione peroxidases, peroxiredoxins, and superoxide dismutase 1) were greater (p < 0.05) in the soleus compared to TA. After one bout of heat, the difference in antioxidant gene expression observed during TN increased (p < 0.05) further between the soleus and TA. In contrast, differences in antioxidant gene expression between soleus and TA became less apparent following two HS bouts. Overall, this data indicates that HS alters expression of genes associated with antioxidant defense in a skeletal muscle type specific manner. This work was funded by the National Research Initiative Competitive Grant no. 2008‐35206‐18817 from the USDA Cooperative State Research, Education, and Extension Service.