Induction of CYP2E1 in testes of isoniazid-treated rats as possible cause of testicular disorders. Shayakhmetova Ganna M,Bondarenko Larysa B,Voronina Alla K,Anisimova Svitlana I,Matvienko Anatoliy V,Kovalenko Valentina M Toxicology letters Isoniazid is reported to be the most reliable and cost-effective remedy for tuberculosis treatment and prophylaxis among first line anti-tuberculosis drugs. Conventionally, the most common and best studied adverse effect of isoniazid is hepatotoxicity, but as for testicular toxicity the problem has not yet explored extensively. The aim of the study was to identify in vivo influence of isoniazid on induction of testicular cytochrome Р-450 2Е1 (CYP2E1) mRNA expression and enzymatic activity, testes DNA fragmentation, serum total testosterone level, and spermatogenesis indices. The significant induction of CYP2E1 was demonstrated in rat's testes following isoniazid administration, specifically CYP2E1 mRNA expression and p-nitrophenolhydroxylase activity was increased in 28 and 7 times as compared with control, respectively. These changes were accompanied by activating of testicular GST in 32%, changing in levels and character of DNA fragmentation, as well as damaging of the spermatogenic epithelium, decreasing in serum testosterone content (1.62 fold), sperm count (19%), and losing of fertility in comparison with untreated males. We assume that in testes of isoniazid-treated rats CYP2E1 may act as a trigger in generating of reactive oxygen species and other toxic metabolites which subsequently mediates DNA damage, spermatogenesis disturbances, and altered male fertilizing capacity. 10.1016/j.toxlet.2015.02.008