Centanni M, Robbins J
Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
J Clin Invest. 1987 Oct;80(4):1068-72. doi: 10.1172/JCI113162.
Whether Na+ movement through the plasma membrane plays a role in thyroid hormone uptake was investigated in intact rat soleus muscles. After preincubation for 120 min at 37 degrees C in modified Krebs-Ringer bicarbonate containing 140 or 5 mM Na+ plus choline or lithium to maintain osmolarity, muscles were incubated with 50 pM [125I]triiodo-L-thyronine (T3) or [125I]L-thyroxine (T4) for 60 min. T3 uptake was decreased when extracellular Na+ was replaced by either choline or lithium, the amount of decrease corresponding to the specific (or saturable) uptake component. Monensin, an ionophore that stimulates Na+ entry, increased T3 uptake at 140 mM Na+ but not at 5 mM Na+. Amiloride, a Na+/H+ exchange inhibitor, had no effect on T3 uptake under basal conditions or when Na+ was replaced by choline, but reversed the action of lithium. Ouabain, an inhibitor of Na+/K+ ATPase, reduced specific T3 uptake. T4 uptake was unaffected by low extracellular Na+. These results are consistent with a major role of Na+ movement in T3 uptake by skeletal muscle, but not in T4 uptake, and suggest an involvement of membrane pumps in this process.
在完整的大鼠比目鱼肌中研究了钠离子通过质膜的移动是否在甲状腺激素摄取中发挥作用。在含有140或5 mM钠离子加胆碱或锂以维持渗透压的改良Krebs-Ringer碳酸氢盐中于37℃预孵育120分钟后，将肌肉与50 pM [125I]三碘-L-甲状腺原氨酸（T3）或[125I] L-甲状腺素（T4）孵育60分钟。当细胞外钠离子被胆碱或锂替代时，T3摄取减少，减少量与特异性（或可饱和）摄取成分相对应。莫能菌素是一种刺激钠离子进入的离子载体，在140 mM钠离子浓度下增加T3摄取，但在5 mM钠离子浓度下则不然。氨氯吡咪是一种钠离子/氢离子交换抑制剂，在基础条件下或钠离子被胆碱替代时对T3摄取没有影响，但可逆转锂的作用。哇巴因是一种钠离子/钾离子ATP酶抑制剂，可降低特异性T3摄取。低细胞外钠离子对T4摄取没有影响。这些结果与钠离子移动在骨骼肌摄取T3中起主要作用一致，但在T4摄取中并非如此，并表明膜泵参与了这一过程。
