Summary
The potassium permeability characteristics of the lens membranes of the amphibianRana pipiens and the cephalopodSepiola atlantica were compared by electrophysiological techniques. Both membrane systems are much more permeable to potassium than sodium and inSepiola, the membranes behave as a pure selective potassium electrode near the normal resting potential. The amphibian lens electrical conductance behaves as an outward rectifier, the properties of which can be altered in the presence of external caesium and rubidium. The effects observed were interpreted in terms of blocking of conductance by the alkali metals.
The resting conductance ofSepiola lens membranes is much greater than that of the frog and it is not voltage-sensitive. When the external potassium is reduced, however, the conductance decreases and the underlying non-linear properties are revealed. Additions of rubidium, caesium and barium to the external medium further reduce the conductance and the rectifying properties are enhanced. Again these effects are interpreted in terms of a blocking of potassium conductance by these ions.
The different potassium permeability properties of the two systems are discussed in terms of the role of potassium in the regulation of lens internal osmolarity.
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Jacob, T.J.C., Duncan, G. A comparative study of the membrane permeability properties of amphibian and cephalopod mollusc lenses. J Comp Physiol B 154, 333–341 (1984). https://doi.org/10.1007/BF00684439
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DOI: https://doi.org/10.1007/BF00684439