TrxR activity was measured in extracts from 5 × 10⁷ erythrocytes or approximately 10⁶ Jurkat cells, using the modified assay for NADPH-dependent reduction of DTNB to TNB. Percent inhibition was determined by the decrease in activity after pretreatment of cells with 60 μM DNCB for 30 minutes. Data are means ± SE from 3 experiments. For comparison, the standard assay for Jurkat cells²⁶  gave an activity of 1.30 ± 0.09 nmol TNB produced/10⁶ cells per minute (mean ± SE from 3 experiments), indicating that the 2 assays gave comparable results.

The possibility that trace levels of leukocytes were present with the washed erythrocytes cannot be excluded, and thus the measured activity may be an overestimate.