title: Humic substances modify accumulation but not biotransformation of pyrene in salmon yolk-sac fry.
abstract: Humic substances may influence the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in aquatic environment. Relatively little is known how humic substances affect the biotransformation of PAHs in aquatic animals. Here we report how two different types of humic substances affected the accumulation of pyrene, a four-ringed PAH, to yolk-sac fry of landlocked salmon (Salmo salar m. sebago). The accumulation of pyrene to yolk-sac fry tissues was inversely related to humic substance concentration in a short term (72h) exposure. However, the biotransformation of pyrene was not affected by humic substances. Pyrene or humic substances did not induce CYP1A activity in yolk-sac fry tissues contrasting to beta-naphthoflavone, which was used as a positive control. Yolk-sac fry were capable to biotransform pyrene to phase I (1-hydroxypyrene) and phase II (pyrene-1-sulphate) products. Interestingly, glucuronide conjugate (i.e. pyrene-1-glucuronide) was not present in yolk-sac fry tissues. The concentration of parent pyrene and 1-hydroxypyrene remained the same throughout the experiment but the concentration of pyrene-1-sulphate more than doubled from 24 to 72h. This finding suggests that salmon yolk-sac fry are not capable to excrete phase II biotransformation products or the excretion is very slow. Further, this could indicate that early life stage toxicity of many CYP1A inducing compounds is related to accumulation of phase II conjugates in fry tissues.
authors: Laboratory of Aquatic Ecology and Ecotoxicology, Faculty of Biosciences, University of Joensuu, Finland. jani@akvaplan.niva.no
authors: J O
authors: JO
authors: Honkanen
authors: C
authors: C
authors: Wiegand
authors: J V K
authors: JV
authors: Kukkonen
mesh_terms: D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D002250:Carbon Radioisotopes / Q000032:analysis; D002374:Catalase / Q000032:analysis / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis / Q000187:drug effects; D005260:Female; D005618:Fresh Water / Q000032:analysis; D020719:Glucuronides / Q000032:analysis; D005982:Glutathione Transferase / Q000032:analysis / Q000187:drug effects; D006812:Humic Substances; D011721:Pyrenes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D020317:Salmo salar / Q000378:metabolism*; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002250:Carbon Radioisotopes; D020719:Glucuronides; D006812:Humic Substances; D011721:Pyrenes; D014874:Water Pollutants, Chemical; C030984:pyrene; D002374:Catalase; D019363:Cytochrome P-450 CYP1A1; D005982:Glutathione Transferase; C033146:1-hydroxypyrene