An immunohistochemical investigation of the expression of parathyroid hormone receptors in rat cementoblasts

Cementoblasts share many of the features of the osteoblast phenotype. To investigate their expression of cell surface receptors for parathyroid hormone (PTH) (i) unlabelled PTH was bound to tissue sections and subsequently detected with anti-PTH monoclonal antibodies; and (ii) digoxigenin (DIG)-labelled PTH was applied to the sections and the bound hormone detected with anti-DIG antibodies. The use of non-radioactive DIG-labelled PTH represents a novel approach for the immunodetection of PTH receptors in situ. The expression of PTH binding sites by cementoblasts of cellular, but not acellular, cementum was demonstrated. The immunoreactivity was weaker than that seen in osteoblasts, and mainly confined to cementoblasts of fully formed roots. These results suggest that cementoblasts of functional erupted teeth may be responsive to PTH stimulation and further support the idea that cementoblasts and osteoblasts share a similar phenotype.