Effect of Varying Medium Potassium on Lens Volume
Potassium in varying amounts was substituted for sodium in a 305 mOsm saline plus glucose medium. Rat lenses were incubated for 24 hours in the media and the effects on sodium and potassium concentration and on water, sodium and potassium content were determined. Cation potentials and the potential differences across the lens membranes were calculated from the Nernst and Goldman equations. Changes in lens volume are accounted for by changes in the content of potassium with accompanying anion and water. The change in potassium content with increasing potassium in the medium involves two processes — one saturable and identified with the Na, K-pump and one nonsaturable and evident when the pump is saturated. Increases in net potassium content are viewed as being the result of temporary preponderance of potassium influx over efflux that occurs between steady states. A model of volume regulation is described that is consistent with the premises of the double-Donnan model and the data on volume regulation reported for duck red cells.
KeywordsSodium Content Potassium Content Crystalline Lens Saturable Process Donnan Equilibrium
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- Hodgkin, A.L. Ionic movements and electrical activity in giant nerve fibres. Proc. R. Soc. B 148: 1–37 (1957).Google Scholar
- Kinsey, V.E. & K.R. Hightower. Studies on the crystalline lens. XXVI kinetic study showing saturation of the sodium pump. Invest. Ophthal. 17: 186–190 (1978).Google Scholar
- Kinsey, V.E. & I.W. McLean. Studies on the crystalline lens. XVI Characterization of active transport and diffusion of potassium, rubidium and cesium. Invest. Ophthal. 9: 769–784 (1970).Google Scholar
- Kregenow, F.M. Transport in avain red cells, in membrane transport in red cells. (ed. J.C. Ellory and V.L. Lew) Academic Press, N.Y. 1977.Google Scholar
- Patterson, J.W. Effects of amino acid loading on ’Volume Regulation’ in rat lenses. submitted to Expl. Eye Res. (1978).Google Scholar
- Schenk, D., D.J. Fournier & J.W. Patterson. Tissue culture of rat lenses. Proc. Soc. Exper. Biol. Med. 153: 444–448 (1976).Google Scholar