FIGURE 1.
Na,K-ATPase β2 and α2 subunits are localized almost exclusively in T-tubules in cardiomyocytes, whereas the α1 and β1 subunits are localized in both sarcolemma and T-tubules. A, frozen sections of rat heart were double-stained by using mouse antibodies against α1 subunit (green) and rabbit antibodies against α2 subunit (red) (top panels) or by using mouse antibodies against α1 subunit (green) and rabbit antibodies against β2 subunit (red) (bottom panels). Anti-mouse Alexa Fluor 488-conjugated secondary antibodies were used to detect anti-α1 primary antibodies, and anti-rabbit Alexa Fluor 633-conjugated secondary antibodies were used to detect anti-β2 and anti-α2 primary antibodies. The arrows show localization of the α1 subunits, but not of α2 and β2 subunits, in the sarcolemma. The arrowheads show co-localization of α1 and β2 subunits or α1 and α2 subunits in T-tubules. B, frozen sections of human heart were double-stained by using mouse antibodies against β1 subunit (green) and rabbit antibodies against β2 subunit (red). Anti-mouse Alexa Fluor 488-conjugated secondary antibodies were used to detect anti-β1 primary antibodies, and anti-rabbit Alexa Fluor 633-conjugated secondary antibodies were used to detect anti-β2 primary antibodies. The arrows show localization of the β1 subunits, but not of β2 subunits, in the sarcolemma. The arrowheads show co-localization of β1 and β2 subunits in T-tubules. The stealth-like arrowheads show the T-tubules in which the β2 subunits, but not the β1 subunits, are present.