Antioxidant defenses in polar cod (Boreogadus saida) and responsiveness toward dietary crude oil exposure

Abstract

Increasing anthropogenic activities in the Arctic pose the risk for accidental oil spills but our knowledge of ecotoxicological effects is still limited for Arctic organisms. This study aimed to provide insights in baseline levels of antioxidants in polar cod (Boreogadus saida) from different Arctic locations and investigate the susceptibility of this species to oxidative stress during a 32 day dietary crude oil exposure. Baseline levels of individual antioxidants and total oxyradical scavenging capacity (TOSC) varied among different Arctic fjords. Upon crude oil exposure, dose- and time-dependent polycyclic aromatic hydrocarbons (PAHs) biotransformation was evident through hepatic ethoxyresorufine-O-deethylase activity, glutathione S-transferase mRNA expression and biliary PAH metabolites. Changes in the activity of individual antioxidants and TOSC was, however, slight and transient upon exposure. In conclusion, biotransformation was clearly induced by the sub-lethal levels of crude oil in polar cod, while the antioxidant defense responded with high variability.

Effects of dietary crude oil exposure on molecular and physiological parameters related to lipid homeostasis in polar cod ( Boreogadus saida )

“…The dose-dependent response of cyp1a1 towards crude oil treatment showed an up-regulation of xenobiotic detoxification processes in polar cod. This was further supported by Vieweg et al (2017), showing a dose-dependent increase of enzymatic 7-ethoxyresorufin-O-deethylase (EROD) activity and biliary PAH metabolites (naphthalene-and pyrene-type metabolites) in the fish of the same experiment.…”

“…Kobbe crude oil is a light crude oil that is produced and transported in the Barents Sea (Sørheim and Moldestad, 2008), hence a crude oil type that polar cod could be exposed to in a potential oil spill in Arctic waters. The feed preparation for the crude oil treatments and a detailed PAH composition of the fish feed are described in detail in Vieweg et al (2017). Briefly, Calanus sp., a relevant and important natural food of polar cod (Hop and Gjøsaeter, 2013), was mixed with four different doses of crude oil (0, 0.5, 2, 4 mg crude oil/ g feed) without any solvent vehicle with a magnetic stirrer for 5 minutes.…”

“…Samples for molecular and physiological analyses were taken at five time points during the experiment and analyzed for endpoints related to lipid metabolism, reproduction and biotransformation. In addition, samples were also used for a parallel study that examined the effects of crude oil exposure on the antioxidant defense system and further endpoints related to biotransformation processes in polar cod, published in Vieweg et al (2017). As PPARs have been suggested to mediate the adverse effects of PAH exposure on lipid homeostasis in marine organisms (Cajaraville et al 2003, Bilbao et al 2010, the present study included a potent peroxisome proliferator 643 [WY]) as additional treatment in the exposure experiment.…”