Effects of piperonyl butoxide and β‐naphthoflavone on cytochrome P4501A expression and activity in Atlantic salmon ( Salmo salar L.)

• Published in: Environmental Toxicology and Chemistry
• Main Authors: Grøsvik, Bjørn Einar, Larsen, Håvard E., Goksøyr, Anders
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1997
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1002/etc.5620160304; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fetc.5620160304; https://setac.onlinelibrary.wiley.com/doi/pdf/10.1002/etc.5620160304

Abstract The effects of piperonyl butoxide (PBO) and β‐naphthoflavone (BNF) on cytochrome P4501A (CYP1A) expression and activity in juvenile Atlantic salmon ( Salmo salar L.) with regard to time and temperature was investigated. The time exposure study was performed at 8 °C, and the results show that PBO, although acutely functioning as a CYP1A inhibitor, is able to induce CYP1A expression in salmon liver. Both PBO and BNF give highest induction of CYP1A mRNA 48 h after intraperitoneal injection (five‐ and 14‐fold, respectively). The mRNA levels induced by PBO and BNF were sustained during the 8 d of the experiment (four‐ and 11‐fold, respectively). The CYP1A protein content measured by enzyme‐linked immunosorbent assay demonstrated the highest induction by PBO 8 d after exposure (eightfold) and by BNF 4 d after exposure (11‐fold). Activity of CYP1A measured by ethoxyresorufin‐ O ‐deethylase (EROD) demonstrated inhibition after PBO treatment the first 24 h after exposure, followed by threefold induction from 48 h and to the end of the experiment (8 d). β‐Naphthoflavone strongly induced EROD activity, with the highest levels occurring 4 d after treatment (56‐fold) and 8 d after treatment (22‐fold). In the temperature study, the results demonstrated temperature compensation, as salmon acclimated to 7°C for 3 weeks had a significantly higher EROD activity than those acclimated to 11 and 15°C. This was not reflected in significantly higher levels of reduced nicotinamide adenine dinucleotide phosphate cytochrome c reductase activity or CYP1A protein. The inductive properties of PBO and BNF on CYP1A expression was also demonstrated in primary cultures of salmon hepatocytes.