Visualization of proteoglycans and membrane-associated components in rat incisor enamel organ using ruthenium hexammine trichloride.

Ruthenium hexammine trichloride (RHT) revealed granules of proteoglycans in the ground substance of the intercellular spaces of the outer enamel epithelium and stellate reticulum. Strong RHT-positive staining underlined the plasma membrane and filled the narrow intercellular spaces in a zone confined to the stratum intermedium and the basal part of the secretory ameloblasts. In the presecretory ameloblasts, this staining was either faint or absent. Its pattern suggests that proteoglycans and/or other groups of polyanions are functionally implicated in the transport and diffusion that allow delivery of metabolites near the basal part of the secretory ameloblasts.