Immunohistochemical Localization of Gaq, PLCβ, Gαi1-2, PKA, and the Endothelin B and Extracellular Ca2+-sensing Receptors during Early Amelogenesis

Abstract

Antibodies specific to Gaq, PLCβ, Gai 1-2, and PKA were immunohistochemically (IHC) localized in the pre-ameloblasts up to initial dentin matrix deposition and continued in the distal ends of the pre-secretory ameloblasts to the beginning of enamel matrix secretion. It was hypothesized that the endothelin B receptor (ETBR) and/or the extracellular Ca2+-sensing receptor (CaR) would localize in the same locations as their known downstream signal transduction pathway (STP) effectors during events related to early amelogenesis. Localization was similar for the 4 signal transduction pathway elements and the CaR. The ETBR was not localized in any of the cells of the enamel organ. These findings indicate that the CaR and its related STPs are expressed in the pre-ameloblasts and pre-secretory ameloblasts in positions where they may be able to detect increases in extracellular Ca2+ concentrations observed in the pre-dentin matrix in a previous study. These observations are consistent with the hypothesis that increased levels of free Ca2+ in the pre-dentin matrix serve as a primary signal for modification of gene expression important to amelogenesis.