EFFECTS OF RELATIVE HYPOXIA AND HYPERCAPNIA ON INTRACELLULAR PH AND MEMBRANE-POTENTIAL OF CULTURED CAROTID-BODY GLOMUS CELLS

Clusters of glomus cells, isolated from rat carotid bodies, were cultured for up to 2 weeks. Afterwards, we simultaneously measured the intracellular pH (pH(i)) and membrane potentials (E(m)) of single cells with pH-sensitive and KCl-filled microelectrodes. In 89 control cells (bathed in saline equilibrated with 50% O2 in N2) pH(i) was 6.87 +/- 0.014 (SE) and E(m) -36.3 +/- 0.45 mV. In 42 cells, switching to air (about 20% O2) lowered pH(i) in 60% of them by as much as 0.14 unit (mean decrease, 0.05). In the remaining cells, pH(i) increased by as much as 0.18 unit (mean increase, 0.06). Application of 2.5% CO2 in 50% O2 (balance N2) reduced the pH(i) in 90% of 47 cells by as much as 0.44 unit (mean decrease, 0.14). pH(i) increased to a maximum of 0.05 unit (mean increase, 0.04) in the others. Either stimulus depolarized or hyperpolarized glomus cells (-5 to 8 mV) in approximately equal proportions. There was a significant and positive correlation between DELTA-E(m) and DELTA-pH(i). This observation confirms the idea that the E(m) of glomus cell is H+-dependent. Results do not agree with the acidic hypothesis for chemoreception.