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Triphenylmethylphosphonium (TPMP+) as a probe for peritubular membrane potential in the kidney slice
Summary
The lipophilic cation TPMP+ can accurately measure the rabbit kidney basolateral membrane potential after correcting for tissue binding. This validated method provides a reliable tool for studying kidney function.
Area of Science:
- Renal Physiology
- Cellular Electrophysiology
Background:
- The basolateral membrane potential is crucial for kidney function.
- Accurate measurement of this potential is essential for understanding renal transport processes.
Purpose of the Study:
- To validate the use of 3H-tetraphenylphosphonium (TPMP+) as a probe for rabbit kidney basolateral membrane potential.
- To assess the influence of various conditions on TPMP+ distribution and membrane potential.
Main Methods:
- Incubation of rabbit kidney cortical slices with 3H-TPMP+.
- Measurement of slice/medium concentration ratios (S/M) and cell water/medium concentration ratios (C/M) for TPMP+.
- Assessment of TPMP+ distribution under varying K+ concentrations, anaerobic conditions, and TPMP+ concentrations.
- Comparison with microelectrode measurements.
Main Results:
- TPMP+ reached equilibrium S/M of ~20 at 30-50 microM concentrations.
- High TPMP+ concentrations (>50 microM) altered tissue electrolytes and O2 consumption.
- Anaerobic conditions and high K+ reduced S/M TPMP+.
- A tissue binding component for TPMP+ was identified.
- Corrected C/M TPMP+ indicated a Nernst potential of -64 mV, comparable to microelectrode measurements (-54.3 mV).
Conclusions:
- Corrected TPMP+ C/M ratios accurately reflect the steady-state basolateral membrane potential in rabbit kidney slices.
- TPMP+ is a valid probe for assessing basolateral membrane potential when accounting for tissue binding.