Hagfish (Myxine glutinosa) red cell membrane exhibits no bicarbonate permeability as detected by (18)O exchange.

The bicarbonate permeability of the plasma membrane of intact hagfish (Myxine glutinosa) red blood cells and the intracellular carbonic anhydrase activity of these cells were determined by applying the (18)O exchange reaction using a special mass spectrometric technique. When the macromolecular carbonic anhydrase inhibitor Prontosil-Dextran was used to suppress any extracellular carbonic anhydrase activity, the mean intracellular acceleration of the CO(2) hydration/HCO(3)(-) dehydration reaction over the uncatalyzed reaction (referred to as intracellular carbonic anhydrase activity A(i)) was 21 320+/-3000 at 10 degrees C (mean +/- s.d., N=9). The mean bicarbonate permeability of the red blood cell membrane (P(HCO3)-) was indistinguishable from zero. It can be concluded that CO(2) transport within hagfish blood does not follow the classical scheme of CO(2) transport in vertebrate blood. It is suggested that the combination of considerable intraerythrocytic carbonic anhydrase activity and low P(HCO3)- may serve to enhance O(2) delivery to the tissue in the exceptionally hypoxia-tolerant hagfish.