Freeze-fracture electron microscopy of simultaneous odontoblast exocytosis and endocytosis in human permanent teeth.
Replica preparations of dental pulp revealed membrane specializations indicating both exocytosis and endocytosis in the apical part of the odontoblast cell body and the proximal part of the odontoblast process. In tangential fractures, the plasmalemma exhibited protruding spheroids, considered to be the final stage in exocytosis. Other stages observed were plasmalemmal elevations covering underlying vesicles and surrounded by particle-free zones and fusion between vesicles and the cell membrane. Features indicative of endocytosis were plasmalemma studded patchwise with small circular craters 60-70 nm in diameter, often in association with intramembranous particles, and clusters of particles, probably constituting the sites of initiation of endocytotic vesicles in the plasmalemma.
D000293:Adolescent; D000328:Adult; D002462:Cell Membrane / Q000648:ultrastructure; D004705:Endocytosis; D005089:Exocytosis; D005614:Freeze Fracturing; D006801:Humans; D008854:Microscopy, Electron; D009804:Odontoblasts / Q000502:physiology / Q000648:ultrastructure*; D014070:Tooth / Q000502:physiology / Q000648:ultrastructure*