Changes in muscle free carnitine and acetylcarnitine with increasing work intensity in the Thoroughbred horse.
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-1 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.
Harris
R C
RC
Department of Comparative Physiology, Animal Health Trust, Newmarket, Suffolk, England.
Foster
C V
CV
D000108:Acetylcarnitine / Q000378:metabolism*; D000822:Animal Husbandry; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism*; D005260:Female; D005994:Glycerophosphates / Q000378:metabolism; D006736:Horses / Q000502:physiology*; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D005082:Physical Exertion; D012146:Rest
D005994:Glycerophosphates; D007773:Lactates; D019344:Lactic Acid; D000108:Acetylcarnitine; C029620:alpha-glycerophosphoric acid; D002331:Carnitine