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Journal of Experimental Biology, Vol 199, Issue 8 1667-1674, Copyright © 1996 by Company of Biologists
JOURNAL ARTICLES |
JM Weber, G Brichon, G Zwingelstein, G McClelland, C Saucedo, ER Weibel and CR Taylor
Museum of Comparative Zoology, Harvard University, Cambridge, MA 02138, USA.
This paper quantifies the fluxes of fatty acids through the pathways supplying muscle mitochondria with oxidative fuel in exercising dogs and goats. We used continuous infusions of 1-[14C]palmitate and indirect calorimetry to measure fatty acid supply from two sources: the circulation and the triglyceride stores within the muscle cells. Our goal was to determine maximal flux through these two branches of the lipid pathway as key functional parameters for testing the principle of symmorphosis, i.e. that structural capacity is quantitatively matched to functional demand in the oxidative substrate pathways. It is under these rate-limiting conditions that we predict that all of the structural capacity will be used. Maximal rates of fatty acid oxidation were reached at low exercise intensities of 40% Mo2max. Fatty acids from the circulation supplied only a small fraction (15-25%) of the total fat oxidized under these conditions. Although dogs were able to oxidize circulatory fatty acids faster than goats, maximal rates were not in proportion to the 2.2-fold difference in aerobic capacity between the two species. Dogs compensated for their relatively lower use of circulatory fatty acids by oxidizing more triglycerides from lipid droplets in their muscle cells. We conclude that fatty acids from intramuscular triglyceride stores are a major source of fuel during maximal rates of lipid oxidation. Furthermore, it is this branch of the fatty acid pathway that is adapted to the large difference in aerobic capacity between dogs and goats.
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M. M. A. L. Pelsers, P. J. Butler, C. M. Bishop, and J. F. C. Glatz Fatty acid binding protein in heart and skeletal muscles of the migratory barnacle goose throughout development Am J Physiol Regulatory Integrative Comp Physiol, March 1, 1999; 276(3): R637 - R643. [Abstract] [Full Text] [PDF]
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S. Bernard, S. Reidy, G Zwingelstein, and J Weber Glycerol and fatty acid kinetics in rainbow trout: effects of endurance swimming J. Exp. Biol., January 2, 1999; 202(3): 279 - 288. [Abstract] [PDF]
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 G. B. McClelland, P. W. Hochachka, and J.-M. Weber Carbohydrate utilization during exercise after high-altitude acclimation: A new perspective PNAS, August 18, 1998; 95(17): 10288 - 10293. [Abstract] [Full Text] [PDF]
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