EFFECTS OF EXPOSURE TO A COMBINATION OF BETA-NAPHTHOFLAVONE AND RESINACIDS ON BIOTRANSFORMATION ENZYMES IN ATLANTIC SALMON PARR (SALMO-SALAR)

S1 Atlantic salmon parr (Salmo salar) were exposed, by intraperitoneal injection (i.p.), to a mixture of three resin acids (dehydroabietic a cid, isopimaric acid and abietic acid) at a range of concentrations [0 .12, 1.2 and 12 mg (100 g fish weight)(-1), with respect to total resi n acid]. Other groups of fish were given beta-naphthoflavone (BNF, 200 mg kg(-1)) in addition to the resin acid mixture. The total dose admi nistered was divided between two i.p. injections given at 0 and 10 day s, respectively; fish were sampled after 20 days. Fish given the highe st resin acid dose in combination with BNF were moribund after 20 days of exposure. Median plasma bilirubin concentrations were elevated to 96 and 70 mu mol l(-1) in those fish receiving, respectively, 0.12 and 1.2 mg resin acid mixture (100 g fish weight)(-1). Exposure to the re sin acid mixture alone did not induce hepatic cytochrome P450 1A (meas ured as EROD activity). However, in combination with BNF, there was a 103% increase and a 45% decrease in EROD activity in those fish given, respectively, 0.12 mg and 1.2 mg resin acid mixture (100 g fish weigh t)(-1), compared to controls receiving BNF alone. The bilirubin UDP-gl ucuronosyl transferase activity was depressed in fish receiving 1.2 mg resin acid mixture (100 g fish weight)(-1), both in the absence and p resence of BNF. UDP-glucuronosyl transferase activity measured with 4- nitrophenol as substrate showed no significant difference between any of the treatments tested. The experiment emphasizes the need to consid er the interactive effects of chemicals from different pollution sourc es on aquatic organisms.