Adult T-cell leukemia-derived factor (ADF), originally defined as an interleukin-2 receptor inducer, is a human thioredoxin (TRX). ADF/TRX is a conserved multifunctional reductant presumably associated with redox regulation of the cellular environment; it works in vitro as a cytokine, free radical scavenger, activator of transcription factors, and substrate for several enzymes. In the present series of experiments, we studied the expression and intracellular localization of ADF/TRX in mouse kidney from two different renal tubular injury models: a free radical-associated model with ferric nitrilotriacetate (Fe-NTA) and a free radical-independent model with HgCl2. Markers of oxidative damage, such as 8-hydroxy-2'-deoxyguanosine, thiobarbituric acid-reactive substances, and 4-hydroxy-2-nonenal-modified proteins, were significantly increased in kidney from male C57B/6 mice 1 hour after a single intraperitoneal injection of Fe-NTA (5 mg iron/kg). However, in kidney from mice given a subcutaneous injection of HgCl2 (5 mg Hg/kg), none of these markers were increased, despite tubular necrosis with sulfhydryl depletion. In the Fe-NTA model only, Northern and Western blot analyses of the kidney revealed induction of ADF/TRX (> 2.5-fold) after 16 hours and translocation of ADF/TRX from the cytoplasmic to nuclear fraction (> 3.5-fold) after 24 hours. Immunohistochemistry showed a patchy distribution of ADF/TRX in the normal renal proximal tubules. In ex vivo experiments using serial normal kidney frozen sections, it was found that renal proximal tubules with low expression of ADF/TRX were more vulnerable to oxidative stress mediated by Fe-NTA. Collectively, these data suggest that: (a) ADF/TRX is induced and translocated to nuclei by oxidative damage mediated by Fe-NTA in the renal proximal tubules; (b) induction of ADF/TRX is independent of tubular necrosis or sulfhydryl depletion; and (c) ADF/TRX is involved in the cellular defense mechanisms in vivo against oxidative damage.