Vitamin-D-dependent calcium-binding-protein and parvalbumin occur in bones and teeth.

Vit-D-Dependent calcium binding protein and parvalbumin have both been detected in ameloblasts and calcified cartilage by immunohistochemical techniques. These two Ca2+ binding proteins may play a crucial role in the local accumulation of Ca2+ ions during the process of mineralization. The mechanisms underlying the deposition of inorganic substances in bone and teeth during physiologic calcification are still the object of intense debate [1, 2]. The hypotheses concerning the factors controlling the initiation of mineralization can be subdivided into three large categories: enzymatic (or non-enzymatic) local elevation of phosphate and calcium [3,4,5,6,7], enzymatic removal of inhibitors of calcification [8] and direct nucleation of CaPO4 crystals on collagen fibrils [9]. In support of the first line of thought we report here the simultaneous occurrence of two different very high affinity Ca2+ binding proteins [vitamin-D-dependent CaBP = VD CaBP and parvalbumin = PV] in bones and teeth. During the studied age period and with immunohistochemical methods, we detected the proteins only in calcified cartilage of bones and in ameloblasts of teeth. We propose that VDCaBP and PV help increase the Ca2+ concentration at the calcification front in some regions involved in mineral deposition.