Differential Expression of Na+/K+-ATPase Isoforms in Cultured Rodent Cardiac and Skeletal Muscle Cells
Cardiac and skeletal muscle are both known to express more than one isoform of the catalytic subunit of Na+/K+-ATPase (rev. in 6). Moreover, both types of myocytes exhibit changes in a isoform expression as they mature in vivo. In the rat, where the difference between isoforms in ouabain affinity is the most pronounced, the α1 isoform (low-affinity receptor) is the major alpha subunit gene product in the heart (at mRNA and protein levels) throughout all developmental stages, whereas expression of α2 and α3 isoforms is more plastic. The alpha 3 isoform is found primarily in fetal and neonatal heart, and it is replaced by the alpha 2 isoform during postnatal maturation of the animal (2). Expression of Na+/K+-ATPase isoforms in rat skeletal muscle is also complex and plastic in response to various stimuli. Two isoforms of sodium pump with different affinities for ouabain — α1 and α2 — undergo changes in level of expression during development and under some physiological circumstances (1,3).
KeywordsSkeletal Muscle Cell Neonatal Heart Myosin Heavy Chain Gene Postnatal Maturation Striate Muscle Type
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