| Calbindin-D28k is an intracellular soluble vitamin D-dependent calcium binding protein, which has a high affinity for Ca2"1". Previous studies have demonstrated the presence of Calbindin-D28k and its mRNA in mineralized tissues, such as bone and tooth, and suggested the involvement of Calbindin-D28k in the mineralization. Although there have been several hypotheses for the role of Calbindin-D28k, the exact function of this protein is still to be established. Traditionally, Calbindin-D28k has been regarded as calcium transporter or intracellular calcium buffer. But recently, the regulatory effects of Calbindin-D28k have been proposed. Some studies showed that Calbindin-D28k subcellularly co-localized with actin filaments in ameloblasts and odontoblasts. In the present study, the distribution of Calbindin-D28k and actin in tooth germs and adult pulps obtained either from rats or human beings was observed and compared by immunochemical method. To further investigate the relationship between the two proteins, double immunofluorescence method was applied to observe the co-localization of Calbindin-D28k and actin in cultured dental papilla cells, and then, the interaction between the two proteins was clarified by immunoprecipitation technique.1 Distribution of Calbindin-D28k and actin in the development of rat molarsIn this study, fetal rats (17-19 days of gestation) and new born pups (from 1 to 14 days old) were utilized to investigate the localization of Calbindin-D28k and actin in the developing molars. Immunohistochemical- 6 -results showed that Calbindin-D28k was detected only in the whole cytoplasm of the differentiated ameloblasts. However, actin was present in the enamel organ as early as at the bud stage. During the period of hard tissue formation, actin was distributed in the Tome's process of ameloblast and throughout the cytoplasm of odontoblast. In adult rat, odontoblasts were still positively stained for actin but only in the cytoplasm abovethe nucleus. These findings tended to suggest that both Calbindin-D28k and actin could be involved in enamel formation but they might function differently. In addition, actin also participateed in dentin formation.2 Distribution of Calbindin-D28k and actin in rat incisor odontoblastsImmunohistochemical method was adopted for examining and comparing the distribution of Calbindin-D28k and actin in the odontoblasts of rat's continuously erupting lower incisor. The results of the present study demonstrated that Calbindin-D28k and actin shared a similar expression pattern, that is, both proteins were detected in the odontoblasts, particularly in the processes of labial side within the 2/3 crownal portion whereas neither in those of lingual side and apical region. This could indicate that the two proteins could be in close relation to dentin formation.3 Distribution of Calbindin-D28k and actin in burred rat dental pulpsIn order to investigate the expression of Calbindin-D28k and actin during pulp restoration, we established the model of rat tooth injury and examined Calbindin-D28k and actin in healthy pulp and the pulps from 2 hours to 14 days after burred. No immunostaining was found for Calbindin-D28k in all the pulps examined. As for actin, positive staining was localized in odontoblasts and vessel endothelia in the healthy pulp. 2h after injury, the odontoblasts near the exposure point turned negative while the vessel endothelia and the nearby cells were strongly labelled. Such strongly immunoreactive vessels always occurred in the area where pulpitis first attacked in the 8h~5d groups. The present study tended to suggest that actincould play an important role in sustaining the odontoblasts in their specificlining style and physical function, and that its up-regulation in vessels mighthave something to do with the early restoration of pulp after injury.4 Distribution of Calbindin-D28k and actin in healthy and carious humanteeth34 wisdom teeth extracted for therapeutic reasons were collected and divided into three groups: n...
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