Lipid synthesis in rats during cold acclimatization.

Abstract

The effect of cold environment on the biosynthesis of lipids in warm-blooded animals was studied in terms of incorporation of acetate-14C into cholesterol and fatty acids of serum, liver and carcass of rats exposed to cold at 0–2°C, for up to 28 days. The results were compared with those of normothermic rats. In in vivo studies, the serum cholesterol concentration of cold-exposed rats was found to be higher, but the liver cholesterol concentration showed little changes. An initial decrease followed by a slight increase in total lipids of both serum and liver of cold-exposed rats was observed. The specific activity of total lipids from serum and liver and of serum cholesterol was very low during the first few days of cold-exposure but gradually reached normal values. At the end of 28 days the specific activity of serum cholesterol was higher in the case of cold-exposed rats, whereas the specific activity of liver cholesterol was higher for the first few days of exposure and slowly reached normal values in 28 days. In in vitro studies using liver slices from cold-exposed and normothermic rats, the specific activity of both total cholesterol and fatty acids from livers of cold-exposed rats was low during the first few days, but gradually increased and showed1½ times and 3 times activity respectively in cholesterol and fatty acids at the end of 28 days of exposure to cold.