Thyroid hormone regulation of Na,K-ATPase expression.

Active Na,K transport across plasma membranes (mediated by Na,K-ATPase) is stimulated by triiodothyronine (T(3)) in all mammalian tissues responsive to thyroid hormone, and this stimulation has been proposed to account for a substantial fraction of thyroid thermogenesis. The enhancement of Na,K-ATPase activity by T(3) results from increased biosynthesis of Na,K-ATPase subunits and is associated with increased abundance of their encoding mRNAs. In certain target tissues, T(3) preferentially augments the expression of the alpha2 isoform of the enzyme (characterized by its high sensitivity to inhibition by cardiac glycosides). The T(3)-induced increase in Na,K-ATPase subunit mRNA expression has been shown to be mediated by both transcriptional and post-transcriptional mechanisms.