Association between muscle acetyl-CoA and acetylcarnitine levels in the exercising horse.
Treadmill exercise of 2-min duration and increasing intensity resulted in increased formation of acetyl-CoA and acetylcarnitine in working muscle of Thoroughbred horses. At high work intensities a plateau was reached for both acetyl-CoA (approximately 50 mumols/kg dry muscle) and acetylcarnitine (approximately 20 mmol/kg dry muscle). Postexercise concentrations were significantly (P less than 0.001) correlated; [acetylcarnitine] = 349.[acetyl-CoA] + 2.4. The results indicate that approximately 350 mumols acetylcarnitine were accumulated for every 1 mumol acetyl-CoA. Under the conditions of exercise used it is probable that most of the acetyl-CoA formed is generated through the intramitochondrial decarboxylation of pyruvate. The acetyl groups of acetyl-CoA are apparently redistributed throughout the whole cell through formation of acetylcarnitine, which readily transverses the mitochondrial membrane. Despite the redistribution, however, the close correlation between acetylcarnitine and acetyl-CoA would indicate that equilibrium was maintained and that neither acetylcarnitine transferase nor carnitine/acetylcarnitine translocase were rate limiting. There is some question as to whether the changes observed relate directly to exercise itself or to the state in muscle 10 s or more after exercise.
Department of Clinical Chemistry I, Huddinge University Hospital, Karolinska Institutet, Sweden.
J I
JI
Carlin
R C
RC
Harris
G
G
Cederblad
D
D
Constantin-Teodosiu
D H
DH
Snow
E
E
Hultman
D000105:Acetyl Coenzyme A / Q000378:metabolism*; D000108:Acetylcarnitine / Q000378:metabolism*; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives*; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003065:Coenzyme A / Q000378:metabolism; D006736:Horses; D009132:Muscles / Q000378:metabolism*; D005082:Physical Exertion / Q000502:physiology*
D000108:Acetylcarnitine; D000105:Acetyl Coenzyme A; D015500:Chloramphenicol O-Acetyltransferase; D002331:Carnitine; D003065:Coenzyme A