Intracellular potassium activity, potassium equilibrium potential and membrane potential of carotid body glomus cells.

The intracellular potassium activity (ai(K)) of glomus cells in isolated rabbit carotid bodies was measured with potassium ion selective microelectrodes (K+ electrodes). The measurements yielded a mean ai(K) value of 33.0 mM in Hepes-buffered Tyrode's solution equilibrated with 100% O2. This value is significantly higher than that predicted by assuming that K+ ions are passively distributed across the membrane of glomus cells. The relationship between the membrane potential (EM) and the equilibrium potential of K+ ions (EK) at various extracellular potassium activities (ao(K] suggests that K+ ions are not involved in the maintenance of the carotid body glomus cell EM.