To address the effects of SME on the steroidogenesis in Leydig cells, testicular mRNA levels of the steroidogenic pathway genes, 17b-hydroxysteroid dehydrogenase type 3 (17b-HSD3), 3b- hydroxysteroid dehydrogenase type 6 (3b-HSD6), steroidogenic acute regulatory protein (StAR), and NR5A1 [= steroidogenic factor 1(SF1)] were analyzed by real-time RT-PCR. Peroxiredoxin (Prdx) family genes function in the modulation of hydrogen peroxide sig- naling in response to stress factors. Prdx 4 is a thioredoxin-depen- dant peroxidase, expressed only in spermatogenic cells in the testis (Iuchi et al., 2009). To address the antioxidative response in male germ cells in response to stress factors testicular Prdx4 mRNA was examined. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as an endogenous control.