ON THE EFFECT OF THE THYROID ON THE METABOLISM OF FREE FATTY ACIDS AND CHOLESTEROL IN FASTING RATS

Abstract

Fasting markedly influences the effect of l-thyroxine on the metabolism of free fatty acids (FFA) and cholesterol in rats. In fed rats thyroxine raises the FFA content of serum and of adipose tissue and increases the liberation of FFA from the latter; in some animals there also occurs an increase in serum cholesterol. These differences are absent in fasting animals. After 48 hours of fasting, serum FFA and FFA liberation from adipose tissue are higher in controls than in thyroxine-treated animals. Total body oxygen consumption remains increased in thyroxine-treated animals even after 48 hours of fasting. Data are given on changes in glycemia, serum uric acid, and heart weight. Phentolamine in vitro was without effect on the liberation of FFA from adipose tissue either in thyroxine-treated animals or in controls.