Estrogenic influences of estradiol-17b, p-nonylphenol and bis-phenol-A on Japanese Medaka (Oryzias latipes) at detected environmental concentrations

Mature male medaka were continuously exposed to 0.005, 0.0–5 or 1.0 ppb of estradiol-17β (E2 or 0.1, 10 or 100 ppb of p-nonylphenol (NP) or bis-phenol-A (BPA). Female-specific proteins (Fsp) were induced in medaka exposed to 0.005 ppb of E₂, 0.1 ppb of NP, or 10 ppb of BPA. Concentrations of 0.005 pbb of E₂ and 0.1 ppb of NP corresponded to concentrations of these chemicals detected in river water in Japan. The abilities of the 3 chemicals to induce Fsp were E₂> NP> BPA. Embryonic medaka were exposed to E₂, NP and BPA under conditions of static-renewal for 200–230 days until pre-maturity. Survival ratios of medaka exposed to E₂ and NP declined in concentrations more than 25 ppb and 50 ppb, respectively. The groups of medaka exposed to E₂ had individuals with testis-ova or abnormal gonad. There was no male in exposure to 1.0 ppb E₂. When exposed to 100 ppb of NP or BPA, abnormal gonad was also detected. Abnormal anal fin (female-like) was observed in male exposed to 100 ppb of NP. The LC₅₀ values for each of the 3 chemicals were much higher than the concentrations detected in water in the environment—the 3 chemicals were considered to have no lethal effect on medaka in aquatic environments. However, exposures to E₂ or NP at environmental concentrations induced Fsp. BPA also had the ability to affect medaka as an environmental estrogen, although its extrogenic activity was weaker than that of E₂ or NP.