Lectin-binding sites in the growing end of rat incisors

Tooth germs of rat incisors were examined by lectin-histochemistry in the portion from the apical end to enamel forming stage. Tissue sections were prepared from paraformaldehyde-fixed and paraffin-embedded tissues with or without EDTA-decalcification. They were stained with fluorescein-isothiocyanate-labeled (F- for short) lectins and observed by a fluorescent microscope. The boundary between inner enamel epithelia and dental papilla cells was stained with F-Con A, F-MPA and F-PNA. The boundary between the epithelia and dentin was stained with F-Con A and F-MPA. Stratum intermedium cells were stained with F-Con A, F-MPA and F-PNA, and were different in the time when they began to be stained with each lectin during their development. Distal cytoplasm of secretory ameloblasts and odontoblasts were stained with F-MPA and F-Con A, respectively. The staining with these lecting became stronger gradually from the apical to the incisal side. These results suggest that F-MPA and F-Con A are useful as a marker indicating the time when enamel and dentin begins to form, respectively. Distal cytoplasm of secretory ameloblasts was also stained with F-Con A and F-PNA. The odontoblastic layer was stained only with F-Con A, but the dental papilla was stained with F-Con A, F-MPA, and F-PNA. Stellate reticulum and outer enamel epithelia were stained with F-Con A and F-MPA. The comparison of the results from decalcified and non-decalcified tissues showed that the EDTA-decalcification scarcely affected these lectin bindings.