Regulation of Na-pump gene expression in cardiovascular system

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Na, K-ATPase, also called the sarcolemmal Na^+-pump, is a ubiquitous transmembrane protein of mammalian cells that maintains electrochemical Na^+ and K^+ gradients across the plasma membrane and affects excitability, contractility, and cell volume regulation of various kinds of cells. The Na, K-ATPase protein comprises two subunits : a large catalytic alpha-subunit and a smaller glycosylated beta-subunit of unknown function. At least three alpha-subunit isoforms, alpha1, alpha2, and alpha3, have been characterized in rats and humans. Two beta-subunit isoforms, beta1 and beta2, have been identified in rats.In the present research project, we investigated the effects of sodium ion and various hormones on Na, K-ATPase alpha1 and beta1 mRNA expression in the cardiovascular system. Na, K-ATPase mRNA expression was analyzed by Northern blotting and Na^+-pump protein content was analyzed by enzyme-linked immunosorbent assay (ELISA). We have revealed that sodium ion, thyroid hormone, and angiotensin II stimulate Na, K-ATPase alpha1-and beta1-isoform mRNA and protein expression in rat vascular smooth muscle cells, mesangial cells, and cardiac myocytes and regulate contractility, excitability, and volume regulation of these cells.