Altered expression level of calbindin D28k in the periodontal ligament of rat molar in response to changes in occlusal force

The present immunohistochemical study was designed to investigate the alter ation in the expression level of calbindin D28k in the periodontal ligament of the rat molar in response to changes in occlusal force to clarify the p hysiological role(s) of this protein in the ligament. In normal periodontal ligament of the lower first molar, immunoreactivity for calbindin D28k was found in the spindle-shaped cells, presumably fibroblasts, at the alveolar portion of the ligament at the distal side of the mesial root and mesial s ide of the distal root. Following the overload of occlusal force to the upp er first molar by bite-raising, the number and immunoreactivity of the posi tive cells in the periodontal ligament of the lower first molar increased g radually. A more significant increase was detected at 7 d following the bit e-raising compared to the normal animals. When occlusal force was removed b y the extraction of the upper first molar, the expression level of calbindi n D28k in the periodontal ligament of the lower first molar rapidly decreas ed, however a subsequent gradual increase was recognized. Statistical analy sis of the spatial immunoreactivity of calbindin D28k in the periodontal li gament was performed and showed statistically significant differences. The present results suggest that calbindin D28k may play important roles in the homeostasis and cytoprotection of the periodontal fibroblasts against occl usal force.