title: Muscle carnitine metabolism during incremental dynamic exercise in humans.
abstract: The changes in muscle content of carnitine and acetylcarnitine have been studied during incremental dynamic exercise. Six subjects exercised for 10 min on an ergometer at 40 and 75% of their maximal oxygen uptake (VO2 max) and to fatigue at 100% of VO2 max (about 4 min). Muscle samples were taken from the quadriceps femoris muscle at rest and after exercise. Muscle content of free carnitine was (means +/- SE) 15.9 +/- 1.7 mmol kg-1 d.wt (dry weight) at rest and remained unchanged after exercise at low intensity but decreased to 5.9 +/- 0.6 and 4.6 +/- 0.5 mmol kg-1 d.wt after exercise at 75 and 100% of VO2 max respectively. Acetylcarnine content at rest was 6.9 +/- 1.9 mmol kg-1 d.wt and increased during exercise in correspondence with the decrease in free carnitine. Muscle content of pyruvate and lactate was unchanged after exercise at 40% of VO2 max but increased at the higher intensities. The parallel increases in acetylcarnitine, pyruvate and lactate indicate that formation of acetylcarnitine is augmented when the availability of glycolytic three-carbon metabolites is high and is consistent with the idea that acetylcarnitine provides a sink for pyruvate and acetyl CoA. This could be of importance for the maintenance of an adequate level of CoA and thus function of the tricarboxylic acid cycle.
authors.affiliation: Department of Clinical Physiology, Karolinska Institute, Huddinge University Hospital, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Sahlin
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000108:Acetylcarnitine / Q000378:metabolism; D000328:Adult; D002331:Carnitine / Q000378:metabolism*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid
chemical_list: D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D000108:Acetylcarnitine; D000105:Acetyl Coenzyme A; D019289:Pyruvic Acid; D002331:Carnitine