SUN-179 Analysis Of Puberty Onset In Zebrafish Subjected To Chronic Expose Of Low Dose Endocrine Disrupting Chemicals And Mixture

Abstract Disclosure: L. Chung: None. Endocrine-disrupting chemicals (EDCs) are exogenous chemicals that interfere with endocrine system function, leading to adverse effects in organisms and humans. Due to their low biodegradability, EDCs persist in the environment and bioaccumulate through trophic levels. Alkylphenols and bisphenol A (BPA) are common EDCs known to act as estrogen receptor agonists, potentially inducing early puberty. This study investigates the effects of chronic low-dose exposure to estrogenic EDCs and mixtures on sexual maturation in juvenile zebrafish (Danio rerio ), a well-established vertebrate model for developmental biology and endocrine research. Zebrafish embryos were exposed to nonylphenol, octylphenol, and BPA individually and inmixtures at 1 µg/L and 10 µg/L from 20 days post-fertilization (dpf) to 60dpf. Samples were collected at 28, 44, 50, and 60 dpf for gene expression analysis and at 50 and 60 dpf for histologic analysis. Quantitative PCR results showed a progressive increase in kiss1 , kiss2 , and gnrh2 expression in the mixture group over time. The fshb gene showed higher expression in the mixture group at early stages, while lhb expression, initially higher in the nonylphenol group, was later surpassed by the mixture group. Histological analysis revealed no significant differences at 50 dpf; however, by 60 dpf, both the mixture and BPA groups exhibited more advanced gonadal development. In summary, zebrafish chronically exposed to low dose mixtures of EDCs demonstrated enhanced expression of puberty-related genes compared to single-substance exposure. These results suggest potential additive or synergistic effects of EDC mixtures on early puberty onset and sexual maturation in juvenile zebrafish. Keywords: precocious puberty, juvenile zebrafish, gonadaldevelopment, endocrine disrupting chemicals, low dose exposure,mixture EDCs Presentation: Sunday, July 13, 2025