Oxidation suppresses the ATP inhibition of the common gating of CLC-1 channels expressed in Xenopus oocytes. All experiments were performed at a pHi of 6.8. (A) Inhibition of CLC-1 by 3 mM cytoplasmic ATP was consistent throughout a time course of 5 min for a large membrane patch. Voltage protocol B was used, and each circle represents the initial tail current. The recording traces in inset panels are an average of consecutive three traces before (black) and at the end of the 1-min ATP application (red). (B) CuPhe suppresses the ATP effect on CLC-1. Continuous recordings using the same voltage protocol and the large-tip electrode as shown in A. The patch was exposed to CuPhe for 2 min before the second ATP application. (C) Effects of ATP on the steady-state Poc-V curve of CLC-1 before (squares) and after (circles) the CuPhe treatment. Black, control; red, 3 mM ATP (n = 4). (D) Monitoring the ATP sensitivity of CLC-1 in channels from Xenopus oocytes using small-tip electrodes. The voltages of the test pulse and the tail pulse were −40 and −100 mV, respectively. Notice that the spontaneous deterioration of the ATP sensitivity is much faster in the top panel (no reducing reagents in the bath solution) than that in the bottom panel (100 μM DTT in the bath solution).
