Changes of the Rat Dentin Matrix Proteins Affected by Long-term Administration of Hydroxyethylidene-1,1-bisphosphonate (HEBP).

Bisphosphonates are widely known as inhibitors of formation and resorption of mineralized tissues. However, it is uncertain how bisphosphonates affect calcium phosphate precipitation and matrix synthesis in mineralized tissues. Several histological approaches have been done to study hard tissues affected by bisphosphonates. In this study, we used a bisphosphonate for biochemical investigation to study the mechanisms of biological mineralization and considered the effects of the bisphosphonates.Hydroxyethylidene-1, 1-bisphosphonate (HEBP) was administered to rats by subcutaneous injection of 10mg P/kg for seven weeks. The incisors of the rats were removed and the dentin matrix proteins were analyzed biochemically. The amount of matrix proteins was relatively increased in the incisors of the experimental rats, though mineralization of the incisors of the those rats was reduced compared with that of the control rats. Dentin phosphophoryns, unique phosphoproteins of dentin, were also elevated in the experimental rats. Nevertheless, the composition of other non-collagenous proteins of dentin was essentially unchanged by the treatment.Inhibition of mineralization by bisphosphonate may not be mediated by inhibition Of synthesis of noncollagenous matrix proteins, but mainly by inhibition of calcium phosphate deposition. Moreover, it is possible that the synthesis of phosphophoryns was promoted by the treatment.