Immunohistochemical localization of Na+, K(+)-ATPase and calmodulin in rat myocardium

The immunohistochemical localization of Na+, K(+)-ATPase and calmodulin was investigated in rat heart muscle using antiserum against the catalytic subunit of the human kidney Na+, K(+)-ATPase and bovine testis calmodulin at the electron microscopic level. Immunostaining for both Na+, K(+)-ATPase and calmodulin was noted on the plasma membrane and plasmalemmal vesicles of the vascular endothelium and cardiac muscle cells. Calmodulin was also detected in the cytoplasm. These immunohistochemical localizations were evaluated by immunoblot analyses. Such localization of Na+, K(+)-ATPase and calmodulin suggests that they may play an important role in the regulation of Na(+)-Ca++ exchange across the cell membrane.