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Effects of natural and experimental PCB contamination on the mixed-function oxidases in the barbel, Barbus barbus
Hugla, J.L.; Kremers, P.; Thomé, J.-P. (1993). Effects of natural and experimental PCB contamination on the mixed-function oxidases in the barbel, Barbus barbus. Belg. J. Zool. 123(Suppl. 1): 35
In: Belgian Journal of Zoology. Koninklijke Belgische Vereniging voor Dierkunde = Société royale zoologique de Belgique: Gent. ISSN 0777-6276; e-ISSN 2295-0451
Peer reviewed article  
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  • Hugla, J.L.
  • Kremers, P.
  • Thomé, J.-P.
Abstract
    Xenobiotics such as PCB are known to be strong inducers of hepatic mixed-function oxidases (MFO) in fishes, but their effects are often experimentally measured after an intraperitoneal injection, a non natural route. As MFO induction can lead to negative effects on reproduction (by increasing steroids catabolism), it was of interest to compare natural and experimental contamination effects on the oxidase activities. Four year old barbels were contaminated with PC B at environmentally relevant to eight times higher concentrations; the pollutant was either added in food (1.6 to 12 ~g PCB/g D.W.) or dissolved in water (80 or 300 ng PCB/1). After a one-month treatment with environmental concentration in food, no significant induction of oxidases can be observed. However, when food and water contain five or eight times higher concentrations, a significant increase of cytochrome P-450 and oxidase activities can be observed after one or 3 months of exposure. Two P-450 dependent enzymes are particularly sensitive: the 7-ethoxyresorufin O-deethylase (EROD) and the 7-ethoxycoumarin O-deethylase (ECOD). PCB liver concentration is higher in fishes contaminated via food than through direct uptake from water, but no difference of MFO induction is observed according to the way of uptake. During the subsequent period of detoxification in clean water, a decrease of all enzymatic activities is observed within a few weeks. A significant relationship is pointed out between PC B concentration in liver and oxidase activities when measured just at the end of the period of uptake. All P-450 dependent oxidases of wild specimens captured in a PCB contaminated river (the Meuse) show induced activities due to chronic contact with toxicants. However, the level of induction is proportionally lower than in experimental fishes. As it has been proposed, hepatic MFO activities are sensitive indicators of water pollution by PCB. Their possible negative effects on the barbel reproduction are to be studied. J.L.H. acknowledges an IRSIA grant).
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