A histochemical study on lectin binding in the immature enamel and secretory ameloblasts of rat incisors.

Four lectin-fluorescent marker conjugates (Con A-F, MPA-F, PNA-F, WGA-R) were used for visualizing their binding sites on tissue sections by fluorescent microscopy. The immature enamel, Tomes' processes and distal cytoplasm of ameloblasts were stained with MPA-F and WGA-R on paraformaldehyde-fixed and paraffin-embedded tissue sections. The MPA- and WGA-binding glycoconjugates seemed to be main components of the organic enamel matrix because of the intense fluorescence from the tissue sections. The central portion of distal cytoplasm of ameloblasts was stained with PNA-F but the immature enamel and Tomes' processes were not. This suggests the PNA-binding glycoconjugates to be intermediates during the process of modifying their oligosaccharide chains or to be elements of Golgi area. Tomes' processes, the distal cytoplasm and periphery of nuclei of ameloblasts were stained with Con A-F. The Con A-binding glycoconjugates except those localizing on Tomes' processes may also be intermediates and/or intracellular elements like the PNA-binding glycoconjugates. Cells of stratum intermedium were stained with Con A-F, MPA-F and WGA-R. Cells of stellate reticulum and outer enamel epithelium were stained with Con A-F and WGA-R. It was indicated that enamel proteins, major organic components of immature enamel, are highly possible candidates for the MPA- and WGA-binding glycoconjugates.