Fig. 3.

Proton transport in iCell Cardiomyocytes resolved by oscillating extracellular pH electrodes in the presence of low (0.1 mM) extracellular pH buffer power. A: Na/H exchange. Outward proton flux is defined by the presence of an extracellular acidification that occurs in the presence of 140 mM extracellular Na at a pH of 8.2 (0.1 mM Tris) with an internal pH of 6.8, and that is blocked by the Na/H exchanger (NHE1) inhibitor EIPA (10 μM). B: Cl/OH exchange. Outward hydroxyl (or inward proton) flux is defined by the presence of an extracellular alkalinization at pH 6.5 [0.1 mM 2-(N-morpholino)ethanesulfonic acid] that occurs in the complete absence of Na on both membrane sides, absence of bicarbonate on both membrane sides, and absence of Cl in the cytoplasm at a pH of 7.6 and that is fully blocked by substituting extracellular Cl for sulfamate.