Estrogenic effect of dietary 4-tert-octylphenol in rainbow trout (Oncorhynchus mykiss).

The estrogenic effect of dietary 4-tert-octylphenol (octylphenol) in rainbow trout Oncorhynchus mykiss was investigated. Octylphenol was administered orally to sexually immature rainbow trout every second day for 11 days in doses between 0.4 and 50 mgkg(-1)2 d(-1). Plasma vitellogenin was measured at day 0, 6 and 11 and at the end of the experiments, the amounts of octylphenol retained in liver and muscle were determined. Increases in average plasma vitellogenin levels were seen at exposure to 40 mg octylphenol kg(-1) every second day; the most sensitive fish responded to 30 mgkg(-1). Doses below 20 mg octylphenol kg(-1)2 d(-1) had no effect. The ED(50) value for induction of vitellogenin synthesis was 35 mg octylphenol kg(-1)2 d(-1). Only 1 to 2 per thousand of the total amount of octylphenol administered orally over the 11 days experimental period was retained in muscle and liver at the end of the experiment. A clear dose-related increase was observed for concentrations of octylphenol in both liver and muscle of fish exposed to doses between 0.4 and 50 mgkg(-1)2 d(-1). A significant correlation was found between the concentrations of octylphenol in the liver and vitellogenin level in plasma.