Measurement of intracellular chloride activity in mouse liver slices with microelectrodes

Abstract Steady-state membrane potential ( V m ) and intracellular Cl − activity ( a Cl i ) were measured with double-barreled Cl − -selective microelectrodes in mouse liver slices. In bathing solutions (33.8° C) containing pyruvate, glutamate, fumarate, and glucose, V m and a Cl i were −27.6 ± 1.0 mV and 32.6 ± 1.5 mM, respectively. This apparent value of a Cl i exceeded the level required for passive distribution of this ion ( a Cl eq = 26.4 ± 1.3 mM) by 6.2 ± 1.0 mM. This difference was essentially unchanged in experiments where (i) Na + was replaced by choline, (ii) HCO 3 − was removed, and (iii) Cl − was replaced by gluconate. These data argue against the presence of Na + - or HCO 3 − -coupled Cl − transport mechanisms in the plasma membrane of mouse liver cells. This implies that a Cl i is in fact at equilibrium and interference with the response of Cl − -selective microelectrodes by intracellular anions is responsible for the apparent difference between a Cl i and a Cl eq . We found that Cl − -selective microelectrodes containing Corning 477315 ligand are sensitive to taurocholate, a representative bile salt. Their selectivity to taurocholate is about 60-times their selectivity towards Cl − . This suggests that interference of bile acids at concentrations normally present in hepatocytes with determinations of a Cl i can account for the apparent difference a Cl i − a Cl eq .