Measurements of the extracellular potassium concentrations in the isolated rabbit retina with different kinds of potassium-sensitive microelectrodes.
When the dark-adapted isolated rabbit retina has been superfused from one side with a plasma-saline mixture containing 3.5 mM potassium, the extracellular potassium concentration within the dark-adapted retina was significantly higher (4.5-6.1 mM) than the potassium of the superfusate, when measured with an electrode filled with Corning 477317. The substantial difference between the [K+]0 of the perfusate and the [K+]0 within the retina is difficult to explain and could be an instrumental artefact. To probe this possibility measurements have now been repeated using 2 different K+ electrodes, one filled with Corning 477317 and the other filled with a valinomycin-based ion exchanger. With the latter electrodes there was practically no gradient between the [K+]0 in the retina (3.2-4.0 mM) and the potassium concentration of the superfusate. It is thus evident that the earlier enigmatic values for [K+]0 relate to the use of Corning 477317-filled K+ electrodes. When, however, changes in [K+]0 were induced by a light stimulus, the measured magnitudes of change in [K+]0 were the same with the 2 types of electrode.
Mättig
W U
WU
Carl-Ludwig-Institute of Physiology, University Leipzig, F.R.G.
Hanitzsch
R
R
D000818:Animals; D004596:Electroretinography / Q000379:methods; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008027:Light; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D014634:Valinomycin
D007202:Indicators and Reagents; D014634:Valinomycin; D011188:Potassium