RESPONSE TO CYANIDE OF 2 TYPES OF GLOMOID CELLS IN MATURE RAT CAROTID-BODY

Cells belonging to glomoids of mature rat carotid bodies were studied using the whole-cell patch clamp technique following acute dissociatio n. The recorded population encompassed two subtypes: one type (n = 202 ), termed G(out), was characterized by a small voltage-dependent inwar d current (43+/-9 pA, mean+/-S.E.M.), large outward current (671+/-31 pA @ +40 mV), high membrane resistance (1910+/-110 MOMEGA) and low cap acitance (5.1+/-0.1 pF). A second subtype (n=56), termed G(in), had si gnificantly lower membrane resistance (177+/-35 MOMEGA), higher membra ne capacitance (15.0+/-1.0 pF) and little voltage-dependent current. N either subtype supported generation of multiple action potentials duri ng depolarization in the current clamp mode. Intracellular staining of the recorded cells by Lucifer yellow showed co-localization of both s ubtypes to clusters of cells which stained positively for catecholamin es. Somal diameter was slightly, but significantly, larger for G(in) c ells (8.7+/-0.4 muM, n = 7) compared to G(out) cells (7.8+/-0.2 muM, n = 31) and all cells had fine cytoplasmic processes extending around n eighboring cells. During recordings using the perforated patch techniq ue, histotoxic hypoxia significantly decreased a voltage-dependent out ward current in G(out) cells by 113+/-60 pA (n = 13), and decreased th e holding current by 10+/-4 pA (n = 13) from a control value of - 32+/ -6 pA. In G(in) cells, cyanide significant decreased membrane resistan ce and decreased holding current by 55+/-28 pA from a control value of + 120+/-42 pA (n = 7), but caused no significant change in outward cu rrent. These results show that glomoids of mature rat carotid bodies c ontain at least two types of cells which differ in their morphologic a nd electrophysiologic characteristics. The subtypes rapidly respond to histotoxic hypoxia and thus may mediate separate roles in the organ r esponse to chemostimuli.