Roncari D A, Murthy V K
J Biol Chem. 1975 Jun 10;250(11):4134-8.
The influence of thyroid hormones on lipid biosynthesis was studied after administration of L-thyroxine to rats for 5 days. Their weights remained the same as those of control animals, despite an approximately 3-fold increment in plasma L-thyroxine and L-triiodothyronine concentrations. The activity of acetyl-CoA carboxylase and fatty acid synthetase as well as incorporation of tritium into fatty acids were depressed significantly in epididymal adipose tissue and enhanced significantly in livers of thyroxine-treated rats. Using antibodies specific against rat liver fatty acid synthetase, it was determined that the changes in activity of this multienzymic complex were due to alterations in amount of enzyme protein. In the presence of optimal concentrations of fatty acids, radioactive sn-glycero-3-phosphate, and co-substrates, total glycerolipid synthesis (defined in this study as the sum of newly formed radioactive mono- and diacyl-sn-glycero-3-phosphate, diglyceride, and triglyceride) was decreased significantly in adipose tissue and increased in liver and heart. Thus, administration of thyroid hormone results in tissue-specific alterations in lipid biosynthesis which, at least in the case of fatty acid synthetase, are due to changes in enzyme protein content.
给大鼠连续5天注射L-甲状腺素后，研究了甲状腺激素对脂质生物合成的影响。尽管血浆L-甲状腺素和L-三碘甲状腺原氨酸浓度增加了约3倍，但它们的体重与对照动物相同。附睾脂肪组织中乙酰辅酶A羧化酶和脂肪酸合成酶的活性以及氚掺入脂肪酸的量显著降低，而甲状腺素处理的大鼠肝脏中则显著增强。使用针对大鼠肝脏脂肪酸合成酶的特异性抗体，确定这种多酶复合物活性的变化是由于酶蛋白量的改变。在脂肪酸、放射性sn-甘油-3-磷酸和共底物的最佳浓度存在下，脂肪组织中总甘油脂质合成（本研究定义为新形成的放射性单酰基和二酰基-sn-甘油-3-磷酸、甘油二酯和甘油三酯的总和）显著降低，而肝脏和心脏中则增加。因此，甲状腺激素的给药导致脂质生物合成的组织特异性改变，至少就脂肪酸合成酶而言，这是由于酶蛋白含量的变化所致。
