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This Article Full Text Full Text (PDF) Corrigendum All Versions of this Article: 107/5/1612    most recent 91651.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Oishi, Y. Articles by Ohira, Y. PubMed PubMed Citation Articles by Oishi, Y. Articles by Ohira, Y.

Heat stress increases myonuclear number and fiber size via satellite cell activation in rat regenerating soleus fibers

¹Laboratory of Muscle Physiology, Faculty of Education, Kumamoto University, Kumamoto, Japan; ; ²Graduate School of Medicine, Osaka University, Osaka, Japan; and ; ³Brain Research Institute and ; ⁴Department of Physiological Science, University of California, Los Angeles, California

Submitted 29 December 2008 ; accepted in final form 24 June 2009

To investigate the effects of heat stress (hyperthermia) on muscle degeneration-regeneration, the soleus muscles of adult male Wistar rats were injected bilaterally with a single injection of bupivacaine. The rats were assigned to a sedentary control (Con), heat stress (Heat), bupivacaine-injected (BPVC), or bupivacaine-injected plus heat stress (BPVC+Heat) group. Heat stress was induced in the Heat and BPVC+Heat groups by immersion of the lower half of the body into water maintained at 42 ± 1°C for 30 min 48 h after the injection of bupivacaine and every other day during the following 1 or 2 wk. The soleus muscles in all groups were excised 24 h after the final bout of heat stress. Mean muscle weight, fiber cross-sectional area, myonuclear number, and heat shock protein 72 (Hsp72) and calcineurin protein levels were lower in the BPVC than in the Con or Heat groups at both time points. In contrast, several of these parameters in the BPVC+Heat group were not different or higher than in the Con or Heat groups at the 1- and/or 2-wk time points. The number of total and activated satellite cells, estimated by analyses of Pax7-negative, M-cadherin-negative, and MyoD-positive nuclei, was greater in BPVC+Heat than in all other groups. Combined, the results indicate that heat stress-related activation of satellite cells and upregulation of Hsp72 and calcineurin expression played important roles in the regeneration of the soleus fibers after bupivacaine injection.

rat soleus; bupivacaine; heat shock protein 72; calcineurin; fiber cross-sectional area