Effect of bicarbonate and other buffers on choroid plexus Na+/K+pump.

The Na+/K+ pump on the apical membrane of the choroid plexus epithelium was found to be sensitive to bicarbonate. Glycodiazine, a non-volatile, lipid soluble buffer with a pK of 5.7, mimicked the effect of bicarbonate, and was transported across the epithelium in the same direction as sodium. These results are explained in terms of a Na+/H+ exchange mechanism on the basal-lateral membrane.