Microcystins-LR impairs zebrafish reproduction by affecting oogenesis and endocrine system

Studies showed that microcystins (MCs) are able to exert negative effects on the reproductive system of animals. However, the major focus of research has been directed toward to male reproductive system and few data are... [ view full abstract ]

Studies showed that microcystins (MCs) are able to exert negative effects on the reproductive system of animals. However, the major focus of research has been directed toward to male reproductive system and few data are available on females. In this study, female zebrafish were exposed to 2, 10, and 50 μg/L of MC-LR for 21 d, and the effects on reproduction, sex steroid hormones, transcription of genes on the hypothalamic-pituitary-gonad (HPG) axis and critical factors in oogenesis were investigated for the first time. Egg production was significantly decreased at ≥10 μg/L MC-LR. MC-LR was identified to increase the concentrations of 17β-estradiol and vitellogenin significantly after 10 μg/L exposure, while decreased the levels of 17β-estradiol, vitellogenin and testosterone in fish after 50 μg/L exposure. The transcriptions of steroidogenic pathway gene (cyp19a, cyp19b, 17βhsd, cyp17 and hmgra) changed as well after the exposure and corresponded well with the alterations of hormones level. A number of intra- and extra-ovarian factors, such as gnrh3, gnrhr1, fshβ, fshr, lhr, bmp15, mrpβ, ptgs2 and vtg1 which regulating oogenesis were significantly changed with a different dose-related effect. Moreover, the maternal exposure resulted in decreased fertilization and hatching rates were also observed and may suggest the possibility of trans-generational effects of MC-LR exposure. The results demonstrate that MC-LR could modulate endocrine function and oogenesis, eventually leading to disruption of reproductive performance in female zebrafish. And these data represent a concrete risk for the aquatic population living in MC polluted areas.