Acetate enhances the chemosensory response to hypoxia in the cat carotid body in vitro in the absence of CO2-HCO3-.

To determine if intracellular acidosis enhances hypoxic chemoreception in the absence of CO2-HCO3- at pH 7.4, the effects of sodium acetate (30 mM) were studied on the chemosensory responses of the cat carotid body to hypoxic, stagnant and cytotoxic hypoxia. Carotid bodies were perfused and superfused in vitro with Tyrode's solution, free of CO2-HCO3-, buffered with HEPES-NaOH, pH 7.40, at 36.5 +/d- 0.5 degrees C and equilibrated at PO2 of 125 Torr (perfusate) and < 20 Torr (superfusate). In the absence of acetate, hypoxia (PO2 25 Torr), flow interruption and NaCN (0.01-100 micrograms) augmented the chemosensory discharges. However, in the presence of acetate, the half-excitation time of these responses decreased and their amplitude increased. Thus, acetate enhances the chemosensory response to hypoxic, stagnant and cytotoxic hypoxia. It is suggested that that intracellular acidosis induced by acetate contributes to this potentiation by correcting the alkaline pHi caused by the absence of HCO3-(-)HCO2 in the perfusate.