In vivo and in vitro metabolism and organ distribution of nonylphenol in Atlantic salmon (Salmo salar)

In the environment, nonylphenol (NP) occurs predominantly as a degradation product of nonylphenol ethoxylate (NPE). They can be found in many types of products including detergents, plastics, emulsifiers, pesticides, and indu strial and consumer cleaning products. Aa a consequence of their use in a v ariety of products, they are quite common in livers and other aquatic envir onments that receive sewage discharges. Because of its enhanced resistance towards biodegradation, toxicity, estrogenic effects, and ability to bioacc umulate in aquatic organisms NTP has been regarded as the most critical met abolite of APEs. We have studied the in vivo and in vitro metabolism and or gan distribution of NP in juvenile salmon. Fish were exposed in vivo to wat erborne [H-3]-4-n-NP for a period up to 72 h or were administered a single oral dose of [H-3]-4-n-NP, In vitro biotransformation of NP was studied by exposure of cultured salmon heyatocytes to [H-3]-1-n-NP in the presence or absence of a CYP1A-inducer, beta-naphthuflavone (beta NF). Our results show that 4-n-NP was mainly metabolized in vivo, to its corresponding glucuroni de conjugates and hydroxylates. The major route of excretion was the bile. The half-life of residues in carcass and muscle was between 24 and 48 h in both waterborne and dietary exposure. In whole body autoradiography, intrag astric administered [H-3]-4-n-NP was mainly present in the gastrointestinal tract and bile. NP-derived radioactivity in fish exposed via water was mor e evenly distributed in the organs compared to intragastric exposure and we re observed in the intestinal contents, liver, kidney, gills, skin, abdomin al fat and brain. In vitro pretreatment of hepatocytes with beta NF had no effect on rates or patterns of NP biotransformation. The in vitro metabolic rate of NP were 118 pmol NP metabolized/h/0.5 x 10(6) cells without beta N F and 98 pmol NP metabolized/h/0.5 x 10(6) cells when beta NF was added to the culture medium. (C) 2000 Elsevier Science B.V. All rights reserved.