Complexing of lipophilic cations and different anions as a possible cause of overestimating the transmembrane potential delta psi as measured by ion-sensitive electrodes.

The transmembrane potential delta psi of isolated rat liver mitochondria was determined by means of a dibenzyl dimethyl ammonium (DDA+)-sensitive electrode and the 86Rb+ distribution after separation by a centrifugation technique under identical incubation conditions. The delta psi determined with the electrode were higher throughout. There was no indication that the lower delta psi measured by means of 86Rb+ distribution were the result of anaerobic events connected with separation of rat liver mitochondria from the medium. The higher delta psi found by using the DDA+-sensitive electrode were due to anion-dependent changes in the activity of DDA+ ions, which were probably caused by complexing between DDA+ and different anions. A procedure was developed to correct the delta psi for this effect. The corrected values were in relatively good agreement with the delta psi obtained from the 86Rb+ distribution.