Figure 5. Voltage and extracellular K+ dependence of ROMK1 channel blockade by internal Mg2+. (A and B) Macroscopic I-V curves of ROMK1 channels recorded in various [Mg2+]int. [K+]int was 100 mM and [K+]ext was as indicated in the figure. (C and D) Fractions of unblocked currents (I/Io) obtained from A and B were plotted against [Mg2+]int for several membrane voltages. Curves superimposed on the data correspond to least-squares fits using I/I0 = MgK obs/ (MgK obs + [Mg2+]int). (E and F) ln MgKobs obtained from C and D were plotted against membrane voltage (Vm). The lines superimposed on the data correspond to least-squares fits using the Woodhull equation, ln MgK obs = ln MgK obs (0 mV) − Mg(zδ)obsF Vm/ RT. (G) MgK (0 mV)obs and Mg(zδ)obs (mean ± SEM, n = 5) for both [K+]ext.
Image published in: Spassova M and Lu Z (1998)
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