ELECTRON MICROSCOPIAL LOCALIZATION OF 5'-NUCLEOTIDASE IN THE RAT PERIPHERAL-NERVE FIBERS BY CERIUM-BASED CYTOCHEMISTRY

To extend our earlier studies on the subcellular distribution of 5'-nu cleotidase in peripheral nerve fibers, we have applied the cytochemica l method with cerium ions as trapping agents for,inorganic phosphate r eleased from adenosine-5'-monophosphate. Adult and 15-day-old Wistar r ats,were investigated. In myelinated nerve fibers, 5'-nucleotidase act ivity was visualized mainly on the Schwann cell plasma membrane, the a xolemma, the surface of the myelin sheath and its widened lamellae in the paranodal areas, and Schmidt-Lanterman clefts. Single reaction pre cipitates were observed at the intraperiod lines of the compact myelin . In addition, in the young animals, the nuclear envelope and the roug h endoplasmic reticulum were also found associated with reaction depos its. The simple axon-Schwann cell sheaths of the unmyelinated nerve fi bers were also reactive. The cerium-based method reveals a pattern of localization of the 5'-nucleotidase in peripheral nerve fibers quite s imilar to that detected by the conventional lead-based method. The cer ium-based method, however, determines a more uniform distribution of f iner reaction deposits along the cellular membranes. In young rats, th e enzyme reaction was found to be more intense, especially in the area s of myelin-forming membranes.