Developmental toxicity and induction of vitellogenin in embryo-larval stages of zebrafish (Danio rerio) exposed to methyl Paraben.

MethylParaben (MP), a methyl ester of p-hydroxybenzoic acid, is used as an anti-microbial preservative in foods, drugs and cosmetics for decades. It enters the aquatic environment, and can have toxic effects on aquatic organisms. Little is known on the developmental toxicity of MP exposure to zebrafish during early life stages. In this study, the developmental effects of MP were evaluated in embryo-larval zebrafish (at concentrations ranging from 100μM, 200μM, 400µM, 800μM and 1000μM for 96h post fertilization (hpf). The survival, hatching, heart beat rate and developmental abnormalities were observed in the embryos exposed to MP. MP exposure resulted in decreased heart rate and hatching rate. Defects including pericardial edema blood cell accumulation and bent spine were observed in all the treated concentration, except at 100μM. With increasing concentrations, the frequency of these defects increased. The 96 hpf LC50 of MP was calculated to be 428μM (0.065mg/L). Furthermore, RT-PCR result showed that in larval zebrafish exposed to 100μM (0.015mg/L) of MP till 96 hpf, expression of vitellogenin I (Vtg -I) was significantly upregulated compared to the control group. This data suggest that even though lower concentrations of MP do not cause phenotypic malformations, it leads to dysregulated expression of estrogenic biomarker gene Vtg-I.