Dye intermediates N-phenyl-2-naphthylamine and o-tolidine are novel environmental androgens with reproductive toxicity in male rats

Endocrine disruptors are environmental chemicals that can interfere with the endocrine system. However, research on endocrine disruptors that interfere with androgen action is still limited. In this study, two new environmental androgens were identified. N-Phenyl-2-naphthylamine (PNA) and o-tolidine are dye intermediates widely used in industry to produce organic pigments. We found that both PNA and o-tolidine activated androgen receptor (AR) transcriptional activity in the luciferase reporter assay and bound to AR-ligand binding domain directly in the surface plasmon resonance analysis. In vivo studies showed that PNA and o-tolidine induced the proliferation of seminal vesicle cells and increased seminal vesicle weight in immature male rats, indicating that these two compounds had androgenic activity in vivo. In addition, in mature male rats, PNA and o-tolidine reduced sperm concentration and motility and increased sperm deformities, and caused atrophy of the seminiferous tubules of the testis and decreased testosterone levels. These results suggest that PNA and o-tolidine are novel environmental androgens, which bind and activate AR and have toxicological effects on male reproductive function.