H₂O₂ and GSH levels in Raji and GSTP1-transfected Raji cells before and after As₂O₃ treatment. (A) Relative H₂O₂ levels in Jurkat and Raji cells. Growth medium was supplemented with 2 μM As₂O₃. After 48 and 72 hours, the intracellular level of H₂O₂ was measured by flow cytometry, as described in “Materials and methods.” *Statistically significant (P < .05) differences, compared with Jurkat cells. (B) Relative H₂O₂ amount in GSTP1-transfected Raji clones. Growth medium was supplemented with 2 μM As₂O₃. After 48 and 72 hours, the intracellular levels of H₂O₂ were measured by flow cytometry. *Statistically significant (P < .05) differences, compared with RV5 and RV7 cell clones. (C) GSH levels in GSTP1-transfected Raji clones. Growth medium was supplemented with 2 μM As₂O₃. After 48 hours, the intracellular level of GSH was measured, as described in “Materials and methods.” (D) H₂O₂ levels and (E) GSH levels after addition of exogenous H₂O₂ at the indicated concentrations into the growth medium of GSTP1-expressing and -nonexpressing Raji cells. After 2 hours, intracellular H₂O₂ and GSH levels were measured, as described in “Materials and methods.”