Effects of exposure to a combination of β-naphthoflavone and resin acids on biotransformation enzymes in Atlantic salmon parr ( Salmo salar)

Abstract

S1 Atlantic salmon parr ( Salmo salar) were exposed, by intraperitoneal injection (i.p.), to a mixture of three resin acids (dehydroabietic acid, 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 resin acid]. Other groups of fish were given β-naphthoflavone (BNF, 200 mg kg −1) in addition to the resin acid mixture. The total dose administered was divided between two i.p. injections given at 0 and 10 days, respectively; fish were sampled after 20 days. Fish given the highest resin acid dose in combination with BNF were moribund after 20 days of exposure. Median plasma bilirubin concentrations were elevated to 96 and 70 μmol l −1 in those fish receiving, respectively, 0.12 and 1.2 mg resin acid mixture (100 g fish weight) −1. Exposure to the resin acid mixture alone did not induce hepatic cytochrome P450 1A (measured 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 weight) −1, compared to controls receiving BNF alone. The bilirubin UDP-glucuronosyl transferase activity was depressed in fish receiving 1.2 mg resin acid mixture (100 g fish weight) −1, both in the absence and presence 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 consider the interactive effects of chemicals from different pollution sources on aquatic organisms.