Metabolism of Adipose Tissue from Normal and Hypothyroid Rats1

The metabolism of adipose tissue from normal and hypothyroid rats was studied in vitro. Oxygen consumption was reduced in fat cells obtained from thyroidectomized rats, but the oxidation of 14C-labeled glucose, pyruvate and acetate proceeded at normal rates. The oxidation of palmitate-1-14C to 14CO2, however, was significantly reduced following thyroidectomy. Synthesis of long-chain fatty acids from a variety of precursors was also reduced in the thyroprivic tissues. In addition to the wellknown reduction in FFA release, thyroidectomy also reduced glycerol production by adipose tissue. Thus, thyroidectomy interferes with the conversion of 2 carbon units to long-chain fatty acids and with the conversion of long-chain fatty acids to 2 carbon fragments. It is suggested that abnormalities in the function of mitochondrial membranes may account for the metabolic defects of thyroidectomy in adipose tissue. (Endocrinology82: 860, 1968)