Effect of nonylphenol on plasma vitellogenin of male adult guppies (Poecilia reticulata).

Adult male guppies (Poecilia reticulata) were exposed to 4-nonylphenol (NP) at nominal concentrations of 10, 60, and 150 microg/L for 7, 14, or 21 days. Significant induction of vitellogenin (VTG) was found in male guppies exposed to 1 microg/L of 17beta-estradiol and 60 or 150 microg/L of NP after 7, 14, or 21 days. Maximum induction was seen after 14 days of treatment at these concentrations. On the other hand, significant induction of VTG in male guppies exposed to 10 microg/L of NP was observed only after 21 days of treatment. A time-dependent tendency of reduction of the gonadosomatic index (GSI) in male guppies treated with 17beta-estradiol or NP was observed, but no corresponding concentration-dependent tendency was detected. There were also no differences in the liver somatic index (LSI) of male fish treated with various concentrations of NP during the above-mentioned exposure periods. Preliminary data presented in this study strongly suggests that measurement of plasma VTG induction in male guppies is a suitable and rather sensitive indicator of exposure to estrogenic chemicals.