The α3 isoform protein of the Na+/K+-ATPase is associated with the sites of neuromuscular and cardiac impulse transmission

In heart and skeletal muscle the sodium pump is crucial for maintenance of membrane potential and cellular integrity. Of the three α-subunit isoforms, α2 and α3 mRNA’s are concentrated in cardiac conduction system (CCS) of normal adult rat (6). We thus studied expression of pump isoform proteins in normal rat heart and skeletal muscle, and in vascular endothelial tissue, using immunofluorescence, immuno-EM, and Western blotting with isoform-specific antibodies.