Proteoglycans (PGs) in the larval amphibian tooth as visualized by cuprolinic blue

Proteoglycans (PGs) were localized in the predentine and dentine of young larvae from the urodelan species Salamandra salamandra. After cuprolinic blue (CB) staining at the critical electrolyte concentration of 0.1 M MgCl2, CB-positive, electron dense filaments with considerable variations in length and width were found in the collagen-free zone adjacent to the odontoblast processes (length up to 1.3 microns, width 21 nm), in predentine (660 nm/3.2 nm), in dentine around (20 nm/9 nm) and in the dentine tubules (35-150 nm/8 nm). Size classes very likely represent different PGs.