Cytochemical investigation of p-NPPase activity in rat cardiac muscle

The cytochemical demonstration of the atrial cardiac myocyte pumping activity has been made by detecting p-nitrophenylphosphatase (NPPase), which is used by investigating of Na(+)-K(+)-ATPase and H(+)-K(+)-ATPase activities. The fine ultrastructural localization of these enzymes was studied using cytochemical methods with cerium as a capturing agent. Na(+)-K(+)-ATPase was localized on the atrial muscle cell plasma membrane, T-tubule membrane, endothelial cell nuclear membrane, and cardiac myocyte nuclear membrane. H(+)-K(+)-ATPase was localized on the atrial muscle cells plasma membrane, T-tubule membrane, and sarcoplasmatic reticulum. The present findings indicate that the transporting metabolic activity of the heart as an endocrine organ is realized by the interaction between p-NPPases.