[Freeze fracturing and thin-section study of intercellular junctions between odontoblasts and the rat incisor....

The study of thin sections and replicas obtained after freeze-fracture showed that the intercellular junctions of the young secretory odontoblasts of the rat incisor were of two types. Zonula adherens (desmosomes) united the cellular bodies at the predentinal border. Ahead of these structures gap junctions were observed. An injection of vinblastine sulfate induced 4h, a) an enlargement of intermembranous spaces between the gap junctions, b) a reduction of the contact surfaces in the desmosomes and c) a thickening of the intracytoplasmic dense material made of microfilaments, associated with the junctional complex. These modifications favoured the observation of these structures after freeze-fracture. The desmosome junctions could play a mechanical function (partitioning of the predentinal compartment) whereas the gap junction allowed the electrotonic coupling of the odontoblasts. They allowed however an intercellular diffusion route for ionic components (calcium) and matrix components of serum origin.