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Table 3 Summary of evidence that has been used to support or oppose the idea of rapid transport of HCO3 following changes in [HCO3 ]plasma at constant pCO2

From: Fluid and ion transfer across the blood–brain and blood–cerebrospinal fluid barriers; a comparative account of mechanisms and roles

For Against
High rate of HCO3 loss from or gain to fluids perfused through the ventricles Little or no change in total CO2 (almost all of which is HCO3 ) in the brain in response to altered [HCO3 ] in plasma
Rapid, easily seen changes in pH (measured by electrodes applied to the brain surface or microelectrodes within the parenchyma) in response to changes in [HCO3 ]plasma Little or no change in pH (measured by electrodes applied to the brain surface or microelectrodes within the parenchyma) in response to changes in [HCO3 ]plasma
Measurable first-pass extraction of H11CO3 from blood No change in intracellular pH measured using 31P-NMR over an hour following decrease in plasma [HCO3 ]
Acute changes in ventilation rate (after denervation of peripheral chemoreceptors) when [HCO3 ]plasma is changed at constant pCO2 low measured permeability to Cl determined using radiotracers