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Human Müller glial cells: altered potassium channel activity in proliferative vitreoretinopathy
A Bringmann1, M Francke, T Pannicke
1Department of Neurophysiology, Paul Flechsig Institute of Brain Research, University of Leipzig, FRG. bria@server3.medizin.uni-leipzig.de
Purpose:
To determine differences of K+ channel activity between Müller glial cells obtained from retinas of healthy human donors and of patients with retinal detachment and proliferative vitreoretinopathy.
Methods:
Müller cells were enzymatically isolated from retinas of healthy donors and from excised retinal pieces of patients. The whole-cell and the cell-attached configurations of the patch-clamp technique were used to characterize the current densities of different K+ channel types and the activity of single Ca2+ -activated K+ channels of big conductance (BK).
Results:
Cells from patients displayed a less negative mean membrane potential (-52.8 mV) than cells from healthy donors (-80.6 mV). However, the membrane potentials in cells from patients scattered largely between -6 and -99 mV. The inwardly rectifying K+ permeability in cells from patients was strongly reduced (0.3 pA/pF) when compared with cells from healthy donors (6.0 pA/pF). At the resting membrane potential, single BK channels displayed a higher mean activity (open probability, Po, and channel current amplitude) in cells from patients (Po, 0.30) than in cells from healthy donors (Po: 0.03). The variations of BK current amplitudes were correlated with the variations of the membrane potential.
Conclusions:
The dominant expression of inwardly rectifying channels in cells from healthy donors is thought to support important glial cell functions such as the spatial buffering of extracellular K+. The downregulation of these channels and the less negative mean membrane potential in cells from patients should impair spatial buffering currents and neurotransmitter clearance. The increased activity of BK channels may support the proliferative activity of gliotic cells via feedback regulation of Ca2+ entry and membrane potential.
Insights
Müller glial cells from patients with retinal detachment show reduced K+ channel function and altered membrane potential compared to healthy donors. This dysfunction may impair glial cell roles and promote cell proliferation.
Area of Science:
- Neuroscience
- Ophthalmology
- Cell Biology
Background:
- Müller glial cells are crucial for retinal function, including K+ homeostasis.
- Retinal detachment and proliferative vitreoretinopathy involve significant cellular changes in the retina.
Purpose of the Study:
- To investigate differences in K+ channel activity in Müller glial cells from healthy human retinas versus those affected by retinal detachment and proliferative vitreoretinopathy.
Main Methods:
- Utilized patch-clamp techniques (whole-cell and cell-attached) on enzymatically isolated Müller cells.
- Characterized K+ channel current densities and single Ca2+-activated K+ channels of big conductance (BK).
Main Results:
- Müller cells from patients exhibited a less negative mean membrane potential (-52.8 mV) compared to healthy donors (-80.6 mV).
- Inwardly rectifying K+ permeability was significantly reduced in patient cells (0.3 pA/pF) versus healthy cells (6.0 pA/pF).
- Single BK channel activity was markedly higher in patient cells (Po=0.30) than in healthy donor cells (Po=0.03).
Conclusions:
- Reduced inwardly rectifying channels in patient cells likely impair spatial buffering of K+ and neurotransmitter clearance.
- Increased BK channel activity in patient cells may contribute to gliotic cell proliferation through feedback mechanisms.