ELECTROPHYSIOLOGICAL AND IMMUNOCYTOLOGICAL DEMONSTRATION OF CELL-TYPE-SPECIFIC RESPONSES TO HYPOXIA IN THE ADULT CAT CAROTID-BODY

We have recently shown two types of cat carotid body cells based on th e oxygen sensitivity of voltage-gated potassium channels. In the prese nt study, we attempted to determine the correlation between cell types (glomus cells, sheath cells, and subtypes of glomus cells) and oxygen sensitivity of potassium channels. Further, changes in membrane poten tials in response to hypoxia were also examined. Carotid body cells ha rvested from adult cats were cultured, and a whole cell patch clamp me thod was applied to determine the oxygen sensitivity of outward curren t. The tested cells were identified by Lucifer Yellow in the patch pip ette. Glomus cells and sheath cells were immunocytochemically identifi ed using tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP) as markers. The cells whose outward current was inhibited by h ypoxia showed TH-immunoreactivity but not GFAP-immunoreactivity. The c ells whose outward current was not sensitive to hypoxia were GFAP-posi tive or TH-negative. One TH-positive cell had oxygen-insensitive outwa rd current. The resting membrane potentials of the cells having oxygen -sensitive outward current were significantly higher (-55 +/- 3 mV) th an those of the cells having oxygen-insensitive outward current (-35 /- 2 mV). The former type of cells was depolarized during hypoxia, but not the latter type of cells. These results suggest that most glomus cells of the adult cat carotid body possess oxygen-sensitive potassium channels and are depolarized in response to hypoxia. On the other han d, sheath cells and possibly a small fraction of glomus cells possess oxygen-insensitive potassium channels and their membrane potential is not affected by hypoxia. (C) 1998 Elsevier Science B.V.