Reproductive dysfunction linked to alteration of endocrine activities in zebrafish exposed to mono-(2-ethylhexyl) phthalate (MEHP)

Abstract This study aimed to investigate whether exposure to mono-(2-ethylhexyl) phthalate (MEHP), one of major metabolite of phthalates that are widespread in the aquatic environment, disrupts the reproductive dysfunction via endocrine activity system in zebrafish. During an exposure period of 21 days, adult zebrafishes were exposed to test concentrations of MEHP (0, 2, 10, and 50 μg/mL) determined by effective concentrations (ECx) for zebrafish embryos. The analytical methods were developed for detecting the activity of steroids using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Exposure to 50 μg/mL of MEHP in female zebrafish significantly decreased the numbers of ovulated eggs and the biosynthetic levels of hepatic vitellogenin mRNA, precursor of yolk protein (VTG), indicating that induces the reproductive dysfunction in female zebrafishes. The biosynthetic levels of steroids, 17β-estradiol, 11-ketotestosterone, and progesterone were remarkably increased in the 50 μg/mL MEHP-exposed group, compared to the control. Interestingly, these parameters for reproductive endocrine activity were altered, along with the elevated levels of cortisol in female zebrafish. However, there was no significant difference between these parameters in male fishes. Therefore, the reproductive dysfunction in female zebrafishes exposed to MEHP is due to alteration of endocrine activities, and this alteration may be closely associated with stress responses, such as the elevated cortisol level. To further understand the impacts of MEHP on reproductive activity of fish, follow-up studies are required to determine the interactions between endocrine activities and stress responses. Taken together, this study provides a methodological approach for assessing reproductive toxicity of endocrine disruptors (EDs) during an exposure period of 21 days, as an alternative to chronic toxicity testing.