Regulation of potassium levels by Müller cells in the vertebrate retina.
The membrane properties of Müller cells, the principal glial cells of the vertebrate retina, have been characterized in a series of physiological experiments on freshly dissociated cells. In species lacking a retinal circulation (tiger salamander, rabbit, guinea pig), the end-foot of the Müller cell has a much higher K+ conductance than do other cell regions. In species with retinal circulation (mouse, cat, owl monkey) the K+ conductance of the end-foot is greater than the conductance of the proximal process of the cell. In these species, however, the K+ conductance of the soma and distal process is equal to, or greater than, the end-foot conductance. Müller cells also possess four voltage-dependent ion channels, including an inward rectifying K+ channel. These membrane specializations may aid in the regulation of extracellular K+ levels by Müller cells in the retina. High end-foot conductance shunts excess K+ out through the end-foot, where it diffuses into the vitreous humor. In vascularized retinae, excess K+ may also be transferred to the ablumenal wall of capillaries, where it could be transported into the blood.
D000818:Animals; D007473:Ion Channels / Q000502:physiology; D009457:Neuroglia / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D013045:Species Specificity
D007473:Ion Channels; D011188:Potassium