Ammonium interaction with the epithelial sodium channel.
N L Nakhoul1, K S Hering-Smith, S M Abdulnour-Nakhoul
1Section of Nephrology, Department of Medicine, Tulane University School of Medicine, 1430 Tulane Ave., New Orleans, Louisiana 70112, USA. nakhoul@tulane.edu
Ammonium chloride (NH4Cl) inhibits mouse epithelial sodium channels (mENaC) in Xenopus oocytes. This finding suggests NH4Cl affects sodium transport, potentially through channel permeability or selectivity, independent of intracellular acidification.
Area of Science:
- Physiology
- Molecular Biology
- Ion Channel Function
Background:
- Mouse epithelial sodium channels (mENaC) are crucial for sodium transport in various tissues.
- Understanding the regulation of mENaC by different chemical compounds is essential for physiological research.
Purpose of the Study:
- To investigate the direct effect of ammonium (NH3/NH4+) on mouse epithelial sodium channels (mENaC).
- To determine if intracellular acidification by NH4Cl contributes to the observed effects on mENaC.
Main Methods:
- Two-electrode voltage-clamp technique in Xenopus oocytes expressing mENaC.
- Ion-selective microelectrodes to measure intracellular pH (pHi) and ion activities.
- Amiloride was used to block mENaC activity.
Main Results:
- NH4Cl significantly reduced Na+ current and hyperpolarization in mENaC-expressing oocytes.
- NH4Cl caused intracellular acidification, but this was not the primary cause of mENaC inhibition.
- Amiloride blocked all Na+ current and voltage changes, confirming mENaC involvement.
Conclusions:
- NH4Cl directly inhibits Na+ transport through mENaC in Xenopus oocytes.
- The inhibitory effect of NH4Cl on mENaC is not mediated by intracellular acidification.
- The permeability and selectivity of ENaC to ammonium may play a role in its regulation.
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