Effect of body temperature during exercise on skeletal muscle cytochrome c oxidase content.
This study determined the role of body temperature during exercise on cytochrome-c oxidase (CytOx) activity, a marker of mitochondrial content, and mitochondrial heat shock protein 70 (mtHSP70), which is required for import of nuclear-coded preproteins. Male, 10-wk-old, Sprague-Dawley rats exercised identically for 9 wk in ambient temperatures of 23 degrees C (n = 10), 8 degrees C with wetted fur (n = 8), and 4 degrees C with wetted fur and fan (n = 7). These conditions maintained exercising core temperature (T(c)) at 40.4, 39.2, or 38.0 degrees C (resting temperature), respectively. During weeks 3-9, exercisers ran 5 days/wk up a 6% grade at 20 m/min for 60 min. Animals were housed at 23 degrees C. Gastrocnemius CytOx activity in T(c)=38.0 degrees C (83.5 +/- 5.5 microatoms O x min(-1) x g wet wt(-1)) was greater than all other groups (P < 0.05), exceeding sedentary (n = 7) by 73.2%. T(c) of 40.4 and 39.2 degrees C also were higher than sedentary by 22.4 and 37.4%, respectively (P < 0.05). Quantification of CytOx content verified that the increased activity was due to an increase in protein content. In extensor digitorum longus, a nonactive muscle, CytOx was not elevated in T(c) = 38.0 degrees C. mtHSP70 was significantly elevated in gastrocnemius of T(c) = 38.0 degrees C compared with sedentary (P < 0.05) but was not elevated in extensor digitorum longus (P > 0.05). The data indicate that decreasing exercise T(c) may enhance mitochondrial biogenesis and that mtHSP70 expression is not dependent on temperature.
Mitchell
Christopher R
CR
Department of Kinesiology, Southwestern University, Georgetown 78626, Texas, USA.
Harris
M Brennan
MB
Cordaro
Anthony R
AR
Starnes
Joseph W
JW
D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D003080:Cold Temperature; D003576:Electron Transport Complex IV / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; C018551:glucose-regulated proteins; D003576:Electron Transport Complex IV