Electron microscopic localization of 5'-nucleotidase in the stratum intermedium and ameloblasts

5'-nucleotidase was demonstrated at the fine structural level in the stratum intermedium and ameloblasts of the first mandibular molars of CD-1 mice. The enzyme was localized with the Wachstein & Meisel (1957) method along the plasma membranes of the cells of the stratum intermedium and ameloblasts. While 5'- nucleotidase was present throughout the stratum intermedium, only the proximal region of the plasma membranes of ameloblasts was demonstrably active for this enzyme. 5'-Nucleotidase has been implicated in transport of metabolites across cell membranes, and its localization in the present study supports this implication as well as the transport functions of the stratum intermedium and the stratum intermedium--ameloblastic interface.