Summary
Treadmill exercise in Thoroughbred horses of 2 min duration and increasing intensity resulted in increased formation and accumulation of acetylcarnitine in the working middle gluteal muscle. At high work intensities a plateau in acetylcarnitine formation was reached corresponding to approximately 70% of the total carnitine pool (approx. 30 mmol · kg−1 dry muscle). Formation of acetylcarnitine was mirrored by an equal fall in the free carnitine content, which stabilised, at the highest work intensities, at around 8 mmol · kg− dry muscle. Acetylcarnitine and carnitine reached their point of maximum change at a work intensity just below that resulting in the rapid production and accumulation of lactate and glycerol 3-phosphate. It is possible that the formation of acetylcarnitine is important in the regulation of the intramitochondrial acetyl CoA/CoA ratio; equally these changes may represent a blocking mechanism aimed at preventing the transfer of unwanted free fatty acids (as acylcarnitines) into the mitochondria at work intensities where they could contribute little to energy production.
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Harris, R.C., Foster, C.V.L. Changes in muscle free carnitine and acetylcarnitine with increasing work intensity in the Thoroughbred horse. Europ. J. Appl. Physiol. 60, 81–85 (1990). https://doi.org/10.1007/BF00846025
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DOI: https://doi.org/10.1007/BF00846025