title: Endurance training induces muscle-specific changes in mitochondrial function in skinned muscle fibers.
abstract: The present study was conducted to investigate the potential role of changes in the apparent K(m) for ADP and in the functional coupling of the creatine (Cr) kinase (CK) system (CK efficiency) in explaining the tighter integration of ATP supply and demand after exercise training. Mitochondrial function was assessed in saponin-skinned fibers from the soleus and the deep red portion of the medial gastrocnemius isolated from trained (T; treadmill running, 5 days/wk, 4 wk) and control (C) female Sprague-Dawley rats. In the soleus, V(max) in the presence of 1 mM ADP was increased by 21% after training (5.9 +/- 0.2 vs. 4.7 +/- 0.4 nmol O(2). min(-1). mg dry wt(-1), P < 0.05). This was accompanied by no change in the K(m) for ADP measured in the absence of Cr (146 +/- 9 vs. 149 +/- 13 microM in T and C, respectively) and in its presence (50 +/- 4 vs. 48 +/- 6 microM in T and C, respectively) and in CK efficiency [K(m) (+Cr)/K(m) (-Cr)]. In contrast, in the red gastrocnemius, training decreased, by 35%, the apparent K(m) for ADP in the absence (83 +/- 5 vs. 129 +/- 9 microM, P < 0.01) of Cr, without affecting V(max) (6.2 +/- 0.4 vs. 6.7 +/- 0.3 nmol O(2). min(-1). mg dry wt(-1) in T and C, respectively) and CK efficiency. These results thus suggest that training induces muscle-specific adaptations of mitochondrial function and that a change in the intrinsic sensitivity of mitochondria to ADP could at least partly explain the tighter integration of ATP and demand commonly observed after training.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4. yburelle@mrl.ubc.ca
authors.forename: Yan
authors.initials: Y
authors.lastname: Burelle
authors.forename: Peter W
authors.initials: PW
authors.lastname: Hochachka
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D003401:Creatine / Q000494:pharmacology; D005260:Female; D006652:Histological Techniques; D066298:In Vitro Techniques; D008931:Mitochondria, Muscle / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D010101:Oxygen Consumption / Q000187:drug effects; D010805:Physical Conditioning, Animal; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
chemical_list: D000244:Adenosine Diphosphate; D003401:Creatine