FIGURE 2.

SKOR current is reversibly enhanced by H₂O₂. A, SKOR current recorded in one HEK293 cell during treatment with 1, 10, and 30 mm H₂O₂ and voltage clamped in repeated 5-s cycles of −50 mV holding (0.8 s), −80 mV conditioning (200 ms), +80 mV test (3 s), and −50 mV tailing (1 s) voltages. Mean ± S.E. are also shown for current amplitudes (○) calculated from the final 0.1 s of each test voltage step and for activation half-times (t½, ●) determined after normalizing current relaxations. Insets (below), expanded current traces from individual clamp cycles taken just before addition of H₂O₂ and near the end of the experiment (indicated by the boxed areas of the main trace). B, mean increase in SKOR current amplitudes from all 23 experiments (cells) as a function of H₂O₂ concentration. Fitting to a simple hyperbolic function yielded an apparent K_d of 3.8 ± 0.6 and maximum 3.0 ± 0.2-fold enhancement. C, representative mean SKOR current enhancement in 10 mm H₂O₂ without (Δ) and with 10 mm glutathione in the patch pipette (●). Subsequent superfusion with buffer alone (wash) had no effect on the enhanced current, but the enhancement could be reversed by adding 10 mm DTT in the bath (▴). No SKOR current enhancement was seen after adding 10 mm DTNB (○) or buffer alone (not shown).