McDonough A A, Brown T A, Horowitz B, Chiu R, Schlotterbeck J, Bowen J, Schmitt C A
Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles 90033.
Am J Physiol. 1988 Feb;254(2 Pt 1):C323-9. doi: 10.1152/ajpcell.1988.254.2.C323.
Synthesis of the sodium pump, Na+-K+-ATPase, is regulated by thyroid hormone in responsive tissues. The purpose of this study was to determine if triiodothyronine (T3) regulates the concentration of the mRNAs coding for the two enzyme subunits, alpha and beta, and the time course of the response. A single dose of T3 (250 micrograms/100 g body wt) was administered to hypothyroid rats that were killed at various times after injection. In the kidney cortexes of the T3-injected animals, as well as hypothyroid and euthyroid rats, alpha- and beta-mRNA concentrations were measured by dot blot using cDNAs corresponding to the two mRNAs; alpha-subunit abundance was measured by Western blot using antibodies to the enzyme, and Na+-K+-ATPase activity was measured enzymatically. alpha- and beta-mRNAs increased coordinately, after a 6-h time lag to 1.6-fold over hypothyroid levels by 12 h after T3. alpha-Subunit abundance increased significantly by 48 h and to 1.4-fold over hypothyroid by 72 h after T3. Na+-K+-ATPase activity increased with the same time course as the increase in alpha-subunit abundance to 1.3-fold over hypothyroid by 72 h after T3. We conclude that T3 regulates Na+-K+-ATPase synthesis and activity by coordinately increasing the mRNAs of both the alpha- and beta-subunits of the enzyme.
钠泵（Na⁺-K⁺-ATP酶）的合成在反应性组织中受甲状腺激素调节。本研究的目的是确定三碘甲状腺原氨酸（T3）是否调节编码该酶两个亚基α和β的mRNA浓度以及反应的时间进程。给甲状腺功能减退的大鼠单次注射T3（250微克/100克体重），并在注射后的不同时间点处死。在注射T3的动物以及甲状腺功能减退和甲状腺功能正常的大鼠的肾皮质中，使用与两种mRNA对应的cDNA通过斑点印迹法测量α和β mRNA的浓度；使用针对该酶的抗体通过蛋白质印迹法测量α亚基的丰度，并通过酶法测量Na⁺-K⁺-ATP酶活性。α和β mRNA在滞后6小时后协同增加，在T3注射后12小时比甲状腺功能减退水平高出1.6倍。α亚基丰度在48小时时显著增加，在T3注射后72小时比甲状腺功能减退水平高出1.4倍。Na⁺-K⁺-ATP酶活性的增加时间进程与α亚基丰度的增加相同，在T3注射后72小时比甲状腺功能减退水平高出1.3倍。我们得出结论，T3通过协同增加该酶α和β亚基的mRNA来调节Na⁺-K⁺-ATP酶的合成和活性。
