Ultrastructural study of the proteoglycans in enamel from rat incisors during late enamel maturation.

The distribution pattern of proteoglycans in the enamel matrix stained by Alcian Blue or by bismuth nitrate was similar to that of its protein components, suggesting that the two are closely associated. Only the most superficial aprismatic zone of enamel was low in these components, whereas they were abundant in prism sheaths. The lack of correlation between the distribution of fibrous structures and that of both crystals and inter-crystalline spaces could be explained by the possibility that, in enamel, proteoglycans exist as amorphous structures.