Microsomal VKORC1 maintains warfarin sensitivity with glutathione reduction. (A) Warfarin inhibition curves of VKORC1 reduced by DTT, GSH, and GSH/GSSG. Error bars are from 3 repeats. (B) Relative IC₅₀ levels. Error bars are calculated from Morrison fitting of the inhibition curves in panel A. The IC₅₀ levels observed with DTT, GSH, and GSH/GSSG are 2.4 ± 0.76 µM, 52 ± 12 nM, and 82 ± 7 nM, respectively.