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. 1998 Apr 1;111(4):601–614. doi: 10.1085/jgp.111.4.601

Figure 5.

Figure 5

Estimation of unitary gluconate current from macroscopic I-V curves. (A) Unitary CFTR channel currents recorded with 154 mM Cl− in the extracellular solution and either 154 mM Cl− (Cl in) or 154 mM gluconate (Gluconate in) in the intracellular solution, at +50 (top) and −50 (bottom) mV. In each case, the line on the left represents the closed state of the channel. At negative potentials with gluconate in the intracellular solution, no single channel activity could be resolved. (B) Mean single channel I-V relationships for CFTR with 154 mM Cl− in the extracellular solution and 154 mM Cl− (○) or gluconate (•) in the intracellular solution. Mean of data from 3–18 patches. Unitary Cl− currents could not be accurately measured with gluconate in the intracellular solution at potentials more negative than −10 mV. (C) Voltage ramp protocol used to examine the effects of intracellular PPi on macroscopic Cl− and gluconate currents. (D) Leak-subtracted macroscopic I-V relationships showing the effect of intracellular PPi on macroscopic Cl− and gluconate currents, recorded with intracellular gluconate and external Cl−. PPi increases current amplitude at all potentials without altering the reversal potential. (E) Raw current traces used to construct the I-V relationships shown in D. Currents were recorded in response to the voltage protocol shown in C.