Anti-androgenic/Estrogenic Effects Of Methyl Parathion On Goldfish (Carassius Auratus)

Methyl parathion (O, O-dimethyl O-4-nitrophenyl phosphorothioate, MP) is anorganphosphorus pesticide with high toxicity. MP could cause reproductive damages,including reduced weight of testis, prostate, pididymis and seminal vesicle in rats anddecreased sperm count and more teratosperm in fish. Furthermore, the endocrinesystem has proved to be responsible for the maintenance reproductive functions andthe generation of germ cells. Thus, in this study, anti-androgenic/estrogenic activitiesof MP were evaluated by determining plasma17β-estradiol (E2) and testosterone (T)levels, induction of vitellogenin (Vtg) protein, and mRNA expressions of VTG,cytochrome P450aromatase (P450arom), androgen receptor (AR), and estrogenreceptor (ER), and reproductive damage induced by MP in adult goldfish (Carassiusauratus) was investigated by examining gonadosomatic index (GSI) and testishistology.(1) Following a21-day exposure of male goldfish to0.001,0.01, and0.1mg/LMP, E2and T levels in the plasma were examined by radioimmunoassay (RIA) andthe mRNA expression of Vtg, P450arom A, and AR was quantified by real-time PCR.The results showed that0.01and0.1mg/L MCP increased plasma E2and T levels,while no obvious changes of either hepatic Vtg mRNA expression or plasma Vtginduction were observed in MP treatments. In addition, mRNA expression levels ofP450arom A (in gonad) and AR (in both liver and gonad) were also decreased by0.01and0.1mg/L MP, indicating the anti-androgen activities of MP on male goldfish.(2) Plasma E2levels were examined by RIA and ERs mRNA expression levels inliver and gonad were quantified by real-time PCR in female goldfish following a21-day exposure to0.001,0.01, and0.1mg/L MP. Results showed that plasma E2levels were significantly increased, and expression levels of ERα mRNA (in liver) andERβ mRNA (in liver and gonad) were up-regulated by0.001and0.01mg/L MP,probably indicating an estrogenic activity of MP on female goldfish.(3) The21-d exposure to0.001,0.01, and0.1mg/L MP caused significantdecrease of GSI in male goldfish, suggesting that the MP delayed the development oftestis. And results of testis histological analysis showed that swelling of Leydig’s and spermatogenous cell,enlargement of interstitial tissues,dissolution of groundmembrane and the decrease of sperm count were observed in0.01and0.10mg/L MPtreatments. Such damage in testis might be directly attributed to declined plasma Tlevels and inhibited gonad AR mRNA expression levels induced by MP.(4) The GSI was increased in female goldfish following a21-day exposure to0.001,0.01, and0.1mg/L MP, probably due to the increased plasma E2levels inducedby MP, by which the weight of ovary was increased abnormally.In conclusion, anti-androgenic/estrogenic activities of MP and its reproductivetoxicities were proved in male and female goldfish. Results showed that MP exhibitedits endocrine disrupting activities at tissue levels, protein levels, and molecular levels.MP could reduce plasma T levels and inhibit transcriptions of P450arom A (in gonad)and AR (in liver and gonad), indicating an anti-androgenic effect on male goldfish.On the other hand, in female goldfish, MP serving as estrogen-like chemicals leadingto increased plasma E2levels and up-regulated mRNA expression levels of ERα (inliver) and ERβ (in liver and gonad). Besides, MP had damaging effects on gonad inboth male and female goldfish, inducing decreased GSI in males and increased GSI infemales.