Intracellular Acidosis Potentiates Carotid Chemoreceptor Responses to Hypoxia in the Absence of CO₂-HCO₃ ⁻

Abstract

Experiments in vitro showed that the frequency of carotid chemosensory discharges (f _x) increases in response to appropriate physiological and pharmacological stimuli in the nominal absence of CO₂-HCO₃ ⁻ (Eyzaguirre & Lewin 1961; Iturriaga & Lahiri, 1991). In studies with isolated glomus cells bathed with media without CO₂-HCO₃ ⁻, hypoxia diminished the membrane K⁺ conductance (López et al, 1989; Peers & Green 1991) and increased intracellular free [Ca²⁺] (Biscoe & Duchen, 1988). Thus, the presence of CO₂-HCO₃₋ in the in vitro medium is not required for the generation of the hypoxic chemosensory response. Nevertheless, the presence of CO₂-HCO₃ ⁻ in the in vitro medium sped up the onset and the rate of rise of the cat chemosensory responses to hypoxia, flow interruption and NaCN, as compared with the responses obtained when the CBs were perfused with medium buffered at the same pH 7.40 (Iturriaga & Lahiri, 1991; Shirahata & Fitzgerald, 1993).