Estrogenic influences of estradiol-17 beta, p-nonylphenol and bis-phenol-Aon 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-17 beta (E-2 or 0.1, 10 or 100 ppb of p-nonylphenol (NP) or bis-p henol-A (BPA). Female-specific proteins (Fsp) were induced in medaka expose d to 0.005 ppb of E-2, 0.1 ppb of NP, or 10 ppb of BPA. Concentrations of 0 .005 pbb of E-2 and 0.1 ppb of NP corresponded to concentrations of these c hemicals detected in river water in Japan. The abilities of the 3 chemicals to induce Fsp were E-2> NP> BPA. Embryonic medaka were exposed to E-2, NP and BPA under conditions of static-renewal for 200-230 days until pre-matur ity. Survival ratios of medaka exposed to E-2 and NP declined in concentrat ions more than 25 ppb and 50 ppb, respectively. The groups of medaka expose d to E-2 had individuals with testis-ova or abnormal gonad. There was no ma le in exposure to 1.0 ppb E-2. When exposed to 100 ppb of NP or BPA, abnorm al 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 environm ent-the 3 chemicals were considered to have no lethal effect on medaka in a quatic environments. However, exposures to E-2 or NP at environmental conce ntrations induced Fsp. BPA also had the ability to affect medaka as an envi ronmental estrogen, although its extrogenic activity was weaker than that o f E-2 or NP.