Effects of two environmental endocrine disruptors di-n-butyl phthalate (DBP) and mono-n-butyl phthalate (MBP) on human sperm functions in vitro

Di-n-butyl phthalate (DBP), a plastic-derived, endocrine-disrupting chemical, is regarded as a male reproductive toxicant. In this study, we investigated the in vitro actions of DBP and mono-n-butyl phthalate (MBP, the main metabolite of DBP) on human sperm functions. Human sperm were treated with DBP (2 nM-6 μM), MBP (1 nM-3 μM), and a mixture of DBP and MBP in vitro. The results showed that only DBP at 6 μM, a dose reported in semen of infertile men, MBP at 3 μM (three times of the reported maximum MBP concentration in semen), and their mixture, had obvious adverse effects on sperm motility, penetration ability and capacitation. In addition, these doses of phthalates suppressed human sperm tyrosine phosphorylation, a key signaling pathway that regulates sperm functions. Our findings indicate that DBP and MBP may compromise human sperm functions by inhibiting sperm tyrosine phosphorylation once they accumulate in semen at high levels.