Abstract
The localization of ouabain sensitive, K+-dependent p-nitrophenylphosphatase (K+-NPPase), a component of the transport adenosine triphosphatase (Na+, K+-ATPase) system, was ultracytochemically investigated in the heminode of Ranvier in the rat optic nerve. K+-NPPase activities were noted on the nodal and paranodal axolemma, and on the paranodal myelin lateral loops. In the nodal region, the axolemma, which lies above the dense cytoplasmic undercoating, showed remarkably strong K+-NPPase activity.
