High Na+ affinity of the Na+,K+ pump in isolated rabbit retinal Müller (glial) cells.
Rabbit retinal Müller (glial) cells were isolated by means of papain and mechanical dissociation. In a special perfusion chamber, the cells were penetrated with a recording microelectrode. Membrane potential changes were recorded in response to extracellular application of both high-K+ solutions and of ouabain, and that during perfusion with normal and Na+-free solutions, respectively. In other Müller cell preparations, Na+,K+-adenosine triphosphatase (ATPase) activity was measured using a radiochemical method, and its Na+ dependence was determined. All results strongly suggest that the Müller cell's Na+,K+ pump can be activated in the presence of extremely low amounts of Na+. This provides additional evidence for significant differences between the glial and the neuronal enzyme.
D000818:Animals; D002463:Cell Membrane Permeability; D008564:Membrane Potentials; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium