Metabolism of Lipids in Rats Exposed to Heat under Conditions of a Normal and a High Fat-High Cholesterol Diet

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Abstract
Prolonged intermittent exposure to heat “34°” exerts strong influence on lipid metabolism in rats maintained with a nutritionally well-balanced diet; a general tendency to decreased cholesterol concentration was observed in the tissues. At the same time a decrease of the biosynthesis of cholesterol from acetate-1-14C occurred in the liver and a decrease of the β-fraction of serum lipoproteins was observed. Exposure to elevated temperature caused a decrease of esterified fatty acid levels in the blood serum and liver; in epididymal fat tissue an increased concentration of these substances took place. The biosynthesis of fatty acids from acetate-1-14C exhibited a marked decrease in the liver. Heat exposure caused a decrease of the iodine number of depot lipids. The decrease of hepatic lipogenesis indicates a general slowing of lipid metabolism under the influence of exposure to elevated temperature. With the high fat-high cholesterol diet no marked differences were noted between the groups investigated, since the markedly unbalanced diet had a more profound metabolic influence than the effect of heat exposure. The morphological picture of the myocardium and aorta was likewise not influenced by heat exposure.