The role of carnitine in the animal exposed to cold

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.