In order to clarify the nature of the fibroblasts from the periodontal ligament, the activity and distribution of alkaline phosphatase (ALPase) and Ca-ATPase was examined.
The periodontal ligament was removed from both functioning and non-functioning teeth at a local slaughter house. The tissues were fixed in 1% glutaraldehyde-1% paraformaldehyde in cacodylate buffer at 4°C. Tissues were then sliced 40 μm thick on a Vibratome. Serial sections were incubated for either ALPase or Ca-ATPase activities. In order to localize the phosphatase activities by light microscopy, non-fixed, frozen sections were prepared by the Azo-dye method.
A high activity of ALPase was found in the periodontal ligament of both functioning and nonfunctioning teeth. The reaction products of the enzyme were mainly distributed along plasma membranes, Golgi apparatus of the fibroblasts and in the extracellular matrix. A moderate activity of CaATPase was also seen in large numbers of fibroblasts in periodontal ligament of both functioning and non-functioning teeth. This enzyme activity was localized mainly on the plasma membrane of the fibroblasts and no activity was seen in the extracellular matrix. ALPase and Ca-ATPase of the nonfunctioning tooth showed an higher activity than that of the functioning tooth. These enzyme activities were evenly distributed throughout the ligament near alveolar bone or cementum.
From these observations, it is suggested that the fibroblasts in the periodontal ligament have cytochemical characteristic similar to those of osteoblasts and different from those in the other connective tissues.