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A new double-barrelled, ionophore-based microelectrode for chloride ions
1Zentrum der Physiologie, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt, Federal Republic of Germany.
Pflugers Archiv : European Journal of Physiology
|September 1, 1989
Summary
A novel chloride-selective microelectrode offers improved accuracy in measuring intracellular chloride activity. This new electrode overcomes limitations of previous designs, providing more reliable data for biological research.
Area of Science:
- Electrochemistry
- Biophysics
- Physiology
Background:
- Accurate measurement of intracellular chloride activity ([Cl-]i) is crucial for understanding cellular function.
- Existing chloride-selective microelectrodes exhibit limitations in selectivity and accuracy, particularly in the presence of bicarbonate.
- Previous studies may have overestimated intracellular chloride levels due to interference from other ions.
Purpose of the Study:
- To develop and characterize a new chloride-selective microelectrode with enhanced selectivity against bicarbonate and organic anions.
- To compare the performance of the new microelectrode with existing ion-exchanger based electrodes.
- To accurately determine intracellular chloride activity in rabbit renal proximal tubule cells.
Main Methods:
- Fabrication of fine-tip double-barrelled microelectrodes using a novel ionophore (5,10,15,20-tetraphenyl-21H,23H-porphin manganese(III) chloride).
- Electrochemical characterization including slope, resistance, and selectivity coefficient (log KpotCLHCO3) determination.
- In situ measurement of membrane potential and intracellular chloride activity in isolated S3 segments of rabbit renal proximal tubule.
Main Results:
- The new microelectrode demonstrated superior discrimination against bicarbonate compared to ion-exchanger electrodes.
- Microelectrodes exhibited a slope of -52.4 mV, resistance of ~7.10(11) Ω, and log KpotCLHCO3 of -1.40.
- Intracellular chloride activity ([Cl-]i) measured with the new electrode was 35.3 mmol/l, dropping to a residual of 1.20 mmol/l in Cl--free solutions.
- Ion-exchanger electrodes yielded a higher residual [Cl-]i of 10.9 mmol/l under similar conditions.
Conclusions:
- The newly developed chloride-selective microelectrode offers improved accuracy and selectivity for measuring intracellular chloride activity.
- The electrode's performance validates its superiority over existing technologies for biological applications.
- The study refutes previous high intracellular chloride readings in Cl--free solutions, attributing them to electrode interference rather than non-exchangeable chloride.