The pH volume changes of human red cells in vitro due to the exchange of chloride and hydroxyl anions.

In glucose exit experiments measured photoelectrically, the excursions on the chart recorder were found to be larger for exits in media of alkaline pH. This was shown to be due to the addition of a pH volume effect to that of the osmotic shrinkage resulting from the glucose efflux. The pH-dependent volume change also occurred in glucose-free cells and was a linear function of the pH of the medium between pH 6.8 and 9.0. The effect is consistent with the loss (or gain) of chloride in exchange for hydroxyl anions on the band 3 anion transporter and with the buffering of the hydroxyl anions by haemoglobin. The implications for the working of the anion exchanger and for respiratory physiology are discussed.