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Articles in PresS, published online ahead of print February 8, 2002
J Appl Physiol, 10.1152/jap.01024.2001
Submitted on October 11, 2001
Accepted on February 4, 2002
1 Departments of Zoology and Radiology and Sports Medicine Division, University of British Columbia, Vancouver, BC, Canada
* To whom correspondence should be addressed. E-mail: yburelle{at}mrl.ubc.ca.
The present study was conducted to investigate the potential role of changes in the apparent Km for ADP, and in the functional coupling of the creatine kinase system (CK efficiency) in explaining the tighter integration of ATP supply and demand following 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 d/wk, 4 wk) and control (C) female Sprague-Dawley rats. In the soleus, Vmax in the presence of 1 mM ADP was increased by 21 % following training (5.9 ± 0.2 vs 4.7 ± 0.4 nmol O2.min-1.mg-1 dry wt, P<0.05). This was accompanied by no change in the Km for ADP measured in the absence of creatine (146 ± 9 vs 149 ± 13 µM in T and C respectively) and in its presence (50 ± 4 vs 48 ± 6 µM in T and C), and in CK efficiency (Km (+Cr) / Km (-Cr)). In contrast, in the red gastrocnemius, training decreased by 35 % the apparent Km for ADP in the absence (83 ± 5 vs 129 ± 9 µM, P<0.01) of creatine, without affecting Vmax (6.2 ± 0.4 vs 6.7 ± 0.3 nmol O2.min-1.mg-1 dry wtin T and C) and CK efficiency. These results thus suggest that training induce 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 following training.
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