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Apical membrane potassium channels in frog diluting segment: stimulation by furosemide
The American Journal of Physiology
|April 1, 1992
Summary
Frog kidney studies reveal furosemide activates apical potassium channels by increasing their number, not open probability. Amiloride counteracts this, suggesting a role for intracellular pH regulation via the sodium-hydrogen exchanger.
Area of Science:
- Renal Physiology
- Ion Channel Electrophysiology
- Membrane Transport
Background:
- Apical membrane potassium channels are crucial for renal tubule function.
- Understanding their regulation by transport inhibitors is key to deciphering kidney physiology.
Purpose of the Study:
- To investigate the activity of apical membrane potassium channels in frog diluting segments.
- To assess the effects of furosemide and amiloride on these channels.
Main Methods:
- Utilized the patch-clamp technique on isolated frog everted diluting segments.
- Applied cell-attached patches with specific ionic solutions and recorded channel activity.
- Analyzed channel conductance, ion selectivity, voltage dependence, and the impact of inhibitors.
Main Results:
- Identified potassium channels with inward rectification, selective for potassium over sodium, and voltage-dependent open probability.
- Furosemide significantly increased the number of active channels (N) without altering open probability (Po).
- Amiloride inhibited furosemide's effect by reducing N and also reduced N independently, suggesting a link to intracellular pH.
Conclusions:
- Furosemide enhances apical potassium channel activity primarily by increasing the number of channels in the patch.
- Amiloride's inhibitory effect suggests a role for the apical sodium-hydrogen exchanger and intracellular pH in modulating channel availability.