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10:19
Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
Published on: January 10, 2011
Magnesium modulates ROMK channel-mediated potassium secretion.
Lei Yang1, Gustavo Frindt, Lawrence G Palmer
1Department Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY 10065, USA.
Journal of the American Society of Nephrology : JASN
|October 30, 2010
Summary
Physiologic concentrations of magnesium (Mg2+) block outward potassium (K+) currents through ROMK channels from both inside and outside the cell. This Mg2+ block impacts K+ transport, especially during Mg2+ or K+ depletion.
Area of Science:
- Physiology
- Molecular Biology
- Biophysics
Background:
- The role of intracellular and extracellular magnesium (Mg2+) in regulating secretory potassium (K+) currents via Renal Outer Medullary Potassium (ROMK) channels under physiological conditions is not fully understood.
- Understanding Mg2+ interactions with ROMK channels is crucial for comprehending K+ homeostasis and transport regulation.
Purpose of the Study:
- To investigate the blocking effects of intracellular and extracellular Mg2+ on ROMK channel function.
- To determine the influence of varying Mg2+ and K+ concentrations on ROMK channel activity.
Main Methods:
- Expression of ROMK2 channels in Xenopus oocytes.
- Unitary current measurements using inside-out and cell-attached patch-clamp techniques.
- Whole-cell recordings from rat cortical collecting duct principal cells.
Main Results:
- Intracellular Mg2+ (0.2–5 mM) inhibited outward currents at positive membrane potentials (Vm > 0) but not inward currents.
- Extracellular Mg2+ (≥0.2 mM) blocked outward currents in the physiological Vm range (0 to -60 mV).
- Mg2+ block affinity increased as extracellular K+ concentration ([K+]o) decreased, with similar effects observed in native kidney cells.
Conclusions:
- Physiological concentrations of both intracellular and extracellular Mg2+ can modulate secretory K+ currents through ROMK channels.
- These Mg2+-dependent modulations may play a significant role in regulating K+ transport during conditions of K+ and/or Mg2+ depletion.
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