Endothelin receptors and endothelin-1 in developing rat teeth

Introduction: The endothelins area family of small peptides with multiple roles in a variety of tissues. Signaling is mediated through two receptor subtypes, the endothelin A receptor (ETA) specific for Et-1 and the non-specific endothelin B receptor (ETB). Objective: Our goal was to determine the location of immunore activity (IR) for ETA and ETB 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 immunchistochemistry to study developing and mature rat molars and continuously developing incisors. Results: We demonstrate ETA, ETB, and Et-1 expression patterns in teeth, for the first time. ETA 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. ETB 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, ETB-IR was associated with ameloblasts and the stem cell niche of the cervical loop while ETA 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 ETB. Conclusion: The patterns of ETA and ETB 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. (c) 2007 Elsevier Ltd. All rights reserved.