Rates of acetate turnover and lipid synthesis in normal, hypothyroid and hyperthyroid rats

Sodium acetate-1-C14 was administered to anesthetized rats by continuous intravenous infusion, with simultaneous administration of d,l-α-amino-γ-phenylbutyric acid. Radioactivity measurements were made of respiratory CO2, cholesterol, fatty acids and urinary acetylamino acid. From the radioactivity data, calculations were made of rates of acetate turnover and of synthesis of cholesterol and fatty acids from acetate. Data on these metabolic functions are given for normal rats on a stock diet and for animals on a lipid-free ration. Similar experiments were carried out in rats fed thyroid powder and thiouracil. The rate of acetate turnover, and rates of synthesis of cholesterol and fatty acids from acetate, were found to be directly proportional to the basal oxygen consumption rates of the animals. The altered rates of lipid synthesis from acetate resulted, in the main, from absolute changes in rates of the reactions involved, and only to a small extent from shifts in the relative magnitudes of different pathways of acetate metabolism.