Activation of G protein-coupled parathyroid hormone receptors in rat incisor odontoblasts promotes mineralization via cyclic adenosine monophosphate, not Ca signalling: In vitro study.

AIM

Parathyroid hormone (PTH) and its Gα-coupled receptors, PTH receptor, mediate odontoblast differentiation; however, the detailed intracellular adenylyl cyclase-mediated signalling pathway mediated by the PTH-PTH receptor axis remains to be elucidated. Therefore, we measured the intracellular levels of cyclic adenosine monophosphate (cAMP) in living single odontoblasts.

METHODOLOGY

We obtained acutely isolated odontoblasts from newborn Wistar rats and analysed the mineralization ability by Alizarin red staining. Intracellular-free Ca concentration was measured using a fluorescent Ca indicator, whereas intracellular cAMP levels were examined by a mNeon Green-based cAMP sensor.

RESULTS

Granulated PTH was detected in the vascular area of the dental pulp periphery. Application of the non-selective PTH receptor agonist DPC AJ1951 increased cAMP levels in odontoblasts. This increase was significantly inhibited by the non-selective PTH receptor antagonist 4185-v and the adenylyl cyclase inhibitor SQ 22536. However, applying the non-selective PTH receptor agonist DPC AJ1951 did not increase the intracellular Ca concentration without extracellular Ca. In mineralization assays, PTH promoted mineralization by odontoblasts. The mineralization was inhibited by SQ 22536 and 4185-v but not by the phospholipase C inhibitor U73122.

CONCLUSION

Thus, the present study suggests that PTH from the bloodstream functionally activates the Gα-coupled PTH receptor in odontoblasts, which plays an essential role in dentinogenesis.