PARATHYROID-HORMONE-(1-34) RECEPTOR-BINDING AND 2ND-MESSENGER RESPONSE IN RAT INCISOR ODONTOBLASTS

Even though indirect evidence indicates that PTH exerts an anabolic ef fect on dentinogenesis, the existence of PTH receptors and any second- messenger response in odontoblasts have not been demonstrated. The aim of this study was to investigate whether rat incisor odontoblasts exp ress PTH receptors, and to identify which second messenger pathway the hormone may activate. Odontoblasts were dissected from rat incisors. Amino-terminal (1-34) fragment rat PTH [rPTH(1-34)] conjugated to fluo rescein isothiocyanate visualized receptor sites on the cell surface. Upon incubation of odontoblasts with rPTH(1-34), cAMP formation was in creased. However, no fluctuations in intracellular calcium activity we re observed upon rPTH(1-34) stimulation when using Fura-2 as a Ca2+ pr obe. In long-time incubations, stimulation with PTH(1-34) upregulated APase activity. The results demonstrate that rPTH(1-34) evokes an anab olic response in dentinogenically active odontoblasts, and that this m ay be mediated through the protein kinase A/cAMP pathway, whereas no i ndications for Ca2+ as a second messenger were evident.