Immunocytochemical detection of S-100 β in the periodontal Ruffini endings in the rat incisor

Abstract

Subcellular localization of S-100 protein, a kind of calcium binding proteins, was examined immunohistochemically in the Ruffini ending, a primary mechanoreceptor, in the periodontal ligament of the rat incisor. The periodontal ligament of the rat incisor was found to contain many S-100 β- immunoreactive (-IR) structures but no S-100 α-IR elements. The S-100 β-IR structures ramified extensively to form Ruffini endings and were frequently associated with round cells, the terminal Schwann cells, which also showed S-100 β-like immunoreactivity. In many periodontal Ruffini endings, S-100 β-IR products were recognized in the cytoplasm of Schwann cells, but not in the axoplasm. However, some axon terminals which had fewer or shorter axonal fingers, were filled with S-100 β-IR products. The present findings indicated the existence of S-100 β, not S-100 α, in axon terminals of the periodontal mechanoreceptive endings which were identified as type II Ruffini endings.