Immunoelectron microscopic localization of collagenase inhibitor in bovine dentin

The localization of collagenase inhibitor in bovine dentin was investigated by immunohistochemistry and immunoelectron microscopy using a specific rabbit antiserum raised against the inhibitor purified from culture medium of bovine unerupted third molar pulps. Immunoreactive collagenase inhibitor was mainly localized as an amorphous or granular accumulation along the wall of dentinal tubules in decalcified bovine dentin. A part of the immunoreactive inhibitor appeared as two periodic bands on the collagen fibrils surrounding the dentinal tubules. Those two, a major and a minor band, corresponded to D-periodic fibril bands V-VII and I, respectively. As those two bands are located on both borders between overlap and hole zones of the collagen fibril, C- and N-terminal non-helical peptides and eight regions which are nD (n = 1-4) apart from each non-helical peptide along the triple helix are all equally possible binding sites of the collagenase inhibitor on the collagen molecule. It is interesting that the major band is located not exactly at, but fairly close to, the locus of collagenolytic cleavage, which lies between D-periodic fibril bands IV and V.