[Demonstration of lipids by imidazole-buffered osmium tetroxide in the odontoblasts and cells of the enamel organ in the rat incisor].

Tissue post-fixation with imidazole buffered osmium tetroxide allows localization of lipids rich in unsaturated fatty acids (Angermüller and Fahimi, 1982). In odontoblasts, a positive reaction is observed in mitochondria, in membranous structures and in vesicles containing an osmiophilic and amorphous material. In odontoblastic processes, tubulo-vesicular structures and electron-dense coated vesicles seemed to be engaged in endocytosis and transfer processes towards lysosomial structures of the cell body. In the enamel organ, lipidic structures are observed in the stellate reticulum and the stratum intermedium. The plasma membrane of secretory ameloblasts as well as the content of some lysosomial structures are well contrasted. However the distal membranes of the Tomes processes showed weakly stained portions alternating with electron dense segments. Extracellular lipidic globules, sometimes associated with plasma membranes were also seen. These observations demonstrated the alternating weak and strong staining reactions in unsaturated fatty acids of plasma membrane areas of the cell processes, which contrasts with the continuous staining of the plasma membrane of the cell bodies. These observations could be related to functional differences.