Influence of the external concentration of potassium ions on functioning of voltage-dependent potassium channels in GH3 cells

The patch-clamp technique in a whole-cell configuration was used to study the influence of the external concentration of potassium ions on the characteristics of the voltage-dependent potassium current in the plasma membrane of GH₃ cells (a cell line isolated from the rat pituitary body tumor). The [K⁺]_out shift from 5 to 100 mM induced a monotonic increase in potassium current with a constant difference between the testing potential and potassium equilibrium potential. The dependence of an activation time constant, _n, and a steady-state activation,n, of the potassium current on [K⁺]_out is of a distinct non-monotononic character with the extremum at 20 mM. Our experiments and theoretical speculations allow us to suppose that the interaction of potassium ions with slowly relaxing charged channel-forming protein groups induced the observed effects.Neirofiziologiya/Neurophysiology, Vol. 27, No. 2, pp. 110–115, March–April, 1995.