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Potassium accumulation by the glial membrane pump as revealed by membrane potential recording from isolated rabbit
Abstract:
Müller (glial) cells were isolated from rabbit retinae by papaine and mechanical dissociation. In a special perfusion chamber, the cells were penetrated with a recording electrode. When high-K+ solutions were applied into the environment of the cells by means of a second micropipette, the cell membrane depolarized strongly. During prolonged application of high-K+ solutions, however, there occurred a marked repolarization, and after cessation of high-K+ application, a strong hyperpolarization was observed. Both effects disappeared under the influence of ouabain, suggesting the accumulation of intracellular K+ by an active membrane pump. The data were used for calculation of the membrane's Na+:K+ permeability ratio, the intracellular K+ concentration, the pump rate and the mean pump site density. The calculated values are in good agreement with published data from mammalian astrocytes and are compared with those from amphibian Müller cells.
Insights
Rabbit Müller (glial) cells exhibit active potassium (K+) transport via a membrane pump. This pump drives repolarization and hyperpolarization, crucial for retinal cell function and homeostasis.
Area of Science:
- Neuroscience
- Cell Biology
- Ophthalmology
Background:
- Müller glial cells are essential for retinal structure and function.
- Understanding their ion transport mechanisms is key to comprehending retinal physiology.
Purpose of the Study:
- To investigate the ion transport properties of isolated rabbit Müller glial cells.
- To characterize the role of the Na+/K+-ATPase pump in Müller cell responses to potassium.
Main Methods:
- Isolation of Müller glial cells from rabbit retinae using enzymatic and mechanical dissociation.
- Electrophysiological recordings in a perfusion chamber to measure membrane potential changes.
- Application of high-potassium solutions and ouabain to assess pump activity.
Main Results:
- High-potassium application induced initial depolarization followed by repolarization.
- Hyperpolarization was observed after high-potassium removal.
- Ouabain abolished these effects, indicating active K+ accumulation by a pump.
- Calculated membrane permeability ratio, intracellular K+ concentration, pump rate, and pump site density.
Conclusions:
- Rabbit Müller cells possess an active Na+/K+-ATPase pump responsible for K+ homeostasis.
- The pump plays a significant role in regulating membrane potential during and after potassium challenges.
- Findings align with data from mammalian astrocytes and provide insights into glial cell function.