Immunohistochemical identification of cells expressing ATP-gated cation channels (P2X receptors) in the adult rat thyroid

We carried out immunohistochemistry and western blotting of fresh frozen sections and crude extracts from adult rat thyroids. The histochemical and immunoblotting studies were performed with P2X receptor antibodies from 2 different sources. P2X-immunopositive cells were identified by fluorescence double labelling and confocal microscopy. Results of the western blotting experiments showed double bands of approximately 70 kDa and 140 kDa for all 7 P2X receptor subtypes with both sets of antibodies. Histochemical stains with antibodies from both sources also gave essentially identical results. P2X(1), P2X(2) and P2X(6) receptors were detected exclusively in vascular smooth muscle; P2X(5) and P2X(7) receptors were also present on vascular smooth muscle. Endothelial cells stained for P2X(3), P2X(4) and P2X(7) receptors. Thyroid follicular cells displayed immunoreactivity for P2X(3), P2X(4) and P2X(5) receptors. No immunostaining for P2X receptors was observed on C-cells. Possible roles for the broad expression of P2X receptor subtypes in the rat thyroid are discussed.