Endothelin receptors and endothelin-1 in developing rat teeth

Abstract

Introduction The endothelins are a family of small peptides with multiple roles in a variety of tissues. Signaling is mediated through two receptor subtypes, the endothelin A receptor (ET A) specific for Et-1 and the non-specific endothelin B receptor (ET B). Objective Our goal was to determine the location of immunoreactivity (IR) for ET A and ET B in developing and mature rat teeth as indicators of endothelin (Et) regulatory sites and to compare this to the Et-1 (ligand)-IR expression patterns. Design We used immunohistochemistry to study developing and mature rat molars and continuously developing incisors. Results We demonstrate ET A, ET B, and Et-1 expression patterns in teeth, for the first time. ET A was found in developing molar root pulp, pulpal vasculature, and preodontoblasts, and then persisted in odontoblasts or cellular cementocytes at the root apices of mature teeth. ET B was found at the molar (Hertwig's) root sheath during root formation and in molar ameloblasts, nerve fibers and odontoblasts of immature and mature teeth. In incisors, ET B-IR was associated with ameloblasts and the stem cell niche of the cervical loop while ET A was located in the substratum layer. Et-1 was found throughout the dental and periodontal tissues with higher concentrations associated with odontoblasts, nerves and incisor layers that expressed ET B. Conclusion The patterns of ET A and ET B in teeth differ from each other and from those of adjacent tissues suggesting multiple tooth-specific functions for endothelin during development and mature dental function.