A new double-barrelled, ionophore-based microelectrode for chloride ions

Publisher Website
Google Scholar
Abstract
A new Cl− selective microelectrode based on the ionophore 5,10,15,20-tetraphenyl-21H,23H-porphin manganese(III) chloride is presented which discriminates better against HCO 3 − and several organic anions than electrodes containing the Corning 477913 ion-eschanger. Using a redesigned construction procedure, fine-tip double-barrelled microelectrodes were produced which had slopes of −52.4±0.6 mV (SE,n=24), resistances of about 7·1011 Ω and a selectivity coefficient logK Cl, HCO3 pot of −1.40±0.03. Some electrodes showed a small unexplained sensitivity to pH>7.6. When used to puncture cells of isolated S3 segments of rabbit renal proximal tubule during perfusion with HCO 3 − Ringer solution, the electrodes gave a membrane potential of −69.8±1.5 mV and an intracellular Cl− activity, [Cl−]i, of 35.3±2.6 mmol/l. Upon switching bath and lumen perfusions to Cl−-free solutions the “residual” [Cl−]i dropped to 1.20±0.03 mmol/l, while in similar measurements with ion-exchanger electrodes the “residual” [Cl−]i dropped only to 10.9±0.5 mmol/l. These observations demonstrate the superiority of the new electrode and prove that previously determined high [Cl−]i values in Cl−-free ambient solutions reflect interference problems rather than non-exchangeable intracellular chloride.