The role of carnitine in the animal exposed to cold

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Abstract
Changes in the concentrations of carnitine and its derivatives in the liver, heart, and skeletal muscle of rats exposed continuously to 4 °C for periods ranging up to 7 weeks were studied by using a specific enzymatic assay for carnitine. In heart and muscle the concentrations of free carnitine and fatty acylcarnitine were not elevated in cold-acclimatized animals, but that of acetylarnitine increased twofold. In the liver of cold-acclimatized rats, significant increases in all three of the carnitine fractions were observed. The concentration of fatty acylcarnitine in tissues from control animals was greatly elevated by starvation or a high-fat diet but, in contrast, the level was not increased in cold-exposed animals subjected to the same nutritional variants. Normal rats maintained at 22 °C and injected with daily doses of dl-carnitine for 14 days cooled more rapidly and survived for shorter times when exposed to −20 °C than animals injected with saline. Carnitine injections did not alter the oxygen consumption of normal or cold-exposed rats.