Thyroid hormone specifically regulates skeletal muscle Na+-K+-ATPase α2- and β2-isoforms

The purpose of this study was to determine the pattern of thyroid hormone (triiodothyronine, T 3 ) regulation of the Na + -K + -adenosinetriphosphatase (Na + -K + -ATPase) α- and β-subunit expression in skeletal muscle, which expresses α 1 -, α 2 -, β 1 -, and β 2 -subunits, and compare it with that seen in kidney, which expresses only α 1 and β 1 . Three steady states were studied: hypothyroid, euthyroid, and hyperthyroid (hypothyroids injected daily with 1 μg T 3 /g body wt for 2-16 days). Protein and mRNA abundance, determined by Western and Northern analysis, were normalized to a constant amount of homogenate protein and total RNA, respectively