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Vasa recta pericytes express a strong inward rectifier K+ conductance
Chunhua Cao1, Jae Hwan Goo, Whaseon Lee-Kwon
1Division of Nephrology, Department of Medicine, N3W143, 22 S. Greene St., University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
Summary
Strong inward rectifier potassium channels (KIR) and Na+-K+-ATPase influence resting potential in kidney pericytes. KIR channels mediate potassium-induced hyperpolarization in descending vasa recta pericytes.
Area of Science:
- Physiology
- Renal Physiology
- Vascular Biology
Background:
- Strong inward rectifier potassium channels (KIR) are known to be present in vascular smooth muscle cells.
- These channels play a role in K+-induced hyperpolarization, a critical process in regulating vascular tone.
- The presence and function of KIR channels in the descending vasa recta (DVR) microvasculature remain largely uncharacterized.
Purpose of the Study:
- To investigate the presence and function of strong inward rectifier K+ currents in the smooth muscle and pericytes of the isolated descending vasa recta (DVR).
- To determine the contribution of these channels and Na+-K+-ATPase to the resting membrane potential of DVR pericytes.
- To elucidate the role of KIR channels in mediating K+-induced hyperpolarization in DVR pericytes.
Main Methods:
- Whole-cell patch clamp technique was employed on isolated descending vasa recta (DVR) from the kidney.
- Inward currents were measured under varying extracellular potassium (K+) concentrations (5, 50, 140 mmol/l).
- The effects of Ba2+ and Cs+ on these currents were assessed to characterize channel properties and blockade kinetics.
Main Results:
- Increasing extracellular K+ induced Ba2+-sensitive inward rectifying currents in DVR smooth muscle and pericytes.
- These currents reversed at the calculated K+ equilibrium potential, confirming their selective permeability to potassium.
- Ba2+ and Cs+ ions demonstrated voltage-dependent blockade of these currents, with varying binding constants.
- Ba2+ and ouabain significantly depolarized DVR pericytes, while elevated extracellular K+ induced hyperpolarization.
- This K+-induced hyperpolarization was effectively reversed by Ba2+ blockade.
Conclusions:
- Strong inward rectifier K+ channels (KIR) are functionally expressed in DVR pericytes.
- Both KIR channels and Na+-K+-ATPase contribute significantly to establishing the resting membrane potential in DVR pericytes.
- KIR channels are capable of mediating K+-induced hyperpolarization in DVR pericytes, playing a role in regulating their electrical activity.