Cytochrome P 4501 A mRNA and protein induction in the striped bass 1 ( Morone saxatilis ) 2 3

24 The striped bass (Morone saxatilis) support a valuable recreational fishery, and are among the most 25 important piscivorous fish of the San Francisco Estuary. This species has suffered a significant 26 decline in numbers over the past decades and there is indication that contaminants are important 27 contributors. Polycyclic Aromatic Hydrocarbons (PAHs) and Polyhalogenated aromatic 28 hydrocarbons (PHAHs) including PCBs and dioxins are widespread in the Estuary, they typically 29 bioaccumulate through trophic levels, reaching highest levels in top predators, and are known to 30 affect fish health and development. The aim of this study was to investigate the dynamics of 31 cytochrome P4501A (Cyp1a) induction simultaneously at different levels of biological 32 organization (RNA transcription and protein synthesis) as a biomarker of exposure to PAHs and 33 PHAHs. We utilized -naphthoflavone (BNF) as a model PAH to induce Cyp1a responses in 34 juvenile striped bass in both dose-response, and time-response assessments and determined Cyp1a 35 mRNA and protein levels. Significant responses were measured in both systems at 10 mg F.Kg-36 1 , a concentration used for time-response studies. Messenger RNA levels peaked at 6 h post-37 injection, while protein levels increased progressively with time, significantly peaking at 96 h post-38 injection; both remaining elevated throughout the duration of the test (8 days). Our data suggest 39 that rapid induction of gene transcription following exposure and subsequent cumulative protein 40 synthesis could provide a useful means of identifying temporal variants in exposure to Cyp1a 41 inducers in Morone saxatilis. The potential application of this combined Cyp1a gene and protein 42 biomarker in this species for field studies is discussed. 43 44