The Modulation of Intracellular pH in Carotid Body Glomus Cells by Extracellular pH and pCO2

Abstract

The effects of changes in blood pH upon afferent, carotid sinus nerve (CSN) discharge are well documented: a decreased pHo increases firing rate (Gray, 1968; Biscoe, Purves & Sampson; 1970). The mechanisms by which this is brought about, however, remain largely unknown.A number of observations suggest that the type -I, or glomus, cell is the primary site of pH chemoreception (McClodcey, 1968; Ridderstrale & Hanson, 1984; Rigual, Inequez, Carreres & Gonzalez, 1985; Rigual, Lopez-Lopez & Gonzalez, 1991; Rigual, Gonzalez, Gonzalez & Fidone, 1986; Lopez-Lopez et al., 1989; Peers 1990). One of the fundamental questions concerning pH chemoreception is whether these cells respond primarily to a change of extracellular pH or to a secondary change of intracellular pH. We have shown that type-I cells possess at least three pHi-regulatory mechanism which serve, under conditions of constant pHo, to maintain pHi at a fairly constant level of 7.2–7.3 in physiological media (Buckler, Vaughan-Jones, Peers & Nye, 1991a). This has prompted us to determine the extent to which pHi in the type-I cell is influenced by external pH and to consider whether changes of pHi; are required for chemoreception of arterial pH.