Disulfide isomerase activity of AGR2 and intracellular redox state. A) The disulfide isomerase activity of AGR2 was assayed with the insulin precipitation method. The absorbance at 650 nm was plotted against time (minutes). Only dithiothreitol was used as blank. B-C) Levels of GSSG and GSH in Nthy-ori 3–1 AGR2, AGR2 (C → S) and vector control cells were determined using GSH and GSSG assay kit. Values represent the average of duplicate experiments ± standard deviations. D) Nthy-ori 3–1 AGR2, AGR2 (C → S) and vector control cells were incubated H2DCFDA (100 μM) and levels of H2O2 were measured as described in Methods. Asterisks indicate P < 0.001 (***).