Matsumura M, Kuzuya N, Kawakami Y, Yamashita K
Division of Endocrinology and Metabolism, University of Tsukuba, Japan.
Metabolism. 1992 Sep;41(9):995-9. doi: 10.1016/0026-0495(92)90126-U.
It is known that Na-K,adenosine triphosphatase (ATPase) in cell membranes represents an important consumer of cellular energy, eg, adenosine triphosphate (ATP), and that the concentration and activity of this enzyme change in a dose-dependent manner with serum thyroid hormone levels. To examine the hypothesis that low triiodothyronine (T3) syndrome represents a cellular adaptation in generalized severe illnesses that saves tissue energy expenditure, we measured the muscle Na-K,ATPase concentration and its activity in rats that led to low T3 syndrome induced by fasting. The Na-K,ATPase concentration was measured by 3H-ouabain binding to soleus muscle, and its activity was measured by 42K uptake in the contralateral soleus muscle. The effects of refeeding or T3 administration on Na-K,ATPase in soleus muscle in fasted rats were also examined. Na-K,ATPase concentration and activity were both increased in hyperthyroid rats and decreased in hypothyroid rats. In the fasting state, they were decreased to as low as the levels seen in hypothyroidism. Furthermore, with fasting + refeeding or fasting + T3 administration, Na-K,ATPase in soleus muscle returned to the normal level. These results suggest that tissue energy expenditure, as assessed by Na-K,ATPase, in skeletal muscles of fasted rats with low T3 syndrome is actually decreased to levels seen in hypothyroidism, due at least partly to the decrease in serum T3 concentrations, and that there exist some adaptation mechanisms in the peripheral tissues for the accommodation of energy metabolism in the body through decreased thyroxine (T4) to T3 conversion.
已知细胞膜中的钠钾-三磷酸腺苷酶（ATP酶）是细胞能量（如三磷酸腺苷，ATP）的重要消耗者，且该酶的浓度和活性会随着血清甲状腺激素水平呈剂量依赖性变化。为检验低三碘甲状腺原氨酸（T3）综合征代表着全身性严重疾病中的一种细胞适应性变化从而节省组织能量消耗这一假说，我们测量了禁食诱导产生低T3综合征的大鼠肌肉中钠钾-ATP酶的浓度及其活性。钠钾-ATP酶的浓度通过3H-哇巴因与比目鱼肌的结合来测量，其活性通过对侧比目鱼肌对42K的摄取来测量。我们还研究了重新喂食或给予T3对禁食大鼠比目鱼肌中钠钾-ATP酶的影响。甲亢大鼠的钠钾-ATP酶浓度和活性均升高，甲减大鼠则降低。在禁食状态下，它们降低至与甲状腺功能减退时所见水平一样低。此外，通过禁食+重新喂食或禁食+给予T3，比目鱼肌中的钠钾-ATP酶恢复到正常水平。这些结果表明，至少部分由于血清T3浓度降低，低T3综合征禁食大鼠骨骼肌中由钠钾-ATP酶评估的组织能量消耗实际上降低至甲状腺功能减退时所见水平，并且外周组织中存在一些适应机制，可通过减少甲状腺素（T4）向T3的转化来调节体内的能量代谢。
