Immunohistochemical characterization of the rat carotid body.

We studied the histochemical phenotype of carotid body (CB) cells in the adult rat. In addition to tyrosine hydroxylase (TH), type I cells expressed numerous growth factors such as glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor (bFGF), brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), as well as the receptors p75, Ret, epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor-alpha (PDGFR-alpha). Type II cells expressed the glial fibrillary acid protein (GFAP), vimentin, the trophic factor bFGF and receptors p75, EGFR and PDGFR-alpha. Both types I and II cells exhibited a positive immunoreaction to markers of neural progenitor cells such as the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) and nestin, respectively, suggesting that CB contain some immature cells even at the adult stage. The possibility that these cells can be expanded and differentiated into mature neurons should be explored.