Morphological aspects of rat metaphyseal cartilage pericellular matrix

In order to verify whether it is possible to observe morphological evidence of a Ca-P amorphous phase (the first step of Ca-P crystalline deposition), the pericellular area of metaphyseal cartilage was investigated. In the pericellular zone of proliferative, maturation, hypertrophic, degeneration and calcification cartilage, many electron-opaque granules, having a very regular diameter of about 12 nm, disposed in closely-packed chains (chain granules) and increasing in number from the proliferation to the calcification zone, are evident. These chain granules, which are closely connected with proteoglycans, disappear after decalcification and are spatially related to ALPase and ATPase activities. They may be the morphological reflection of the Ca-P amorphous phase.