The Mechanisms of Effects of Oil-Derived Polyaromatic Hydrocarbons on Cardiac Electrical Activity in Navaga Cod (Eleginus nawaga)

Intensive development of oil and gas industries in the Arctic threatens Arctic aquatic ecosystems. Toxic and primarily lethal cardiotoxic effects of oil in living organisms are believed to be associated with polyaromatic hydrocarbons (PAHs), and previous works revealed the electrophysiological mechanisms of action of individual oil-derived PAHs. However, the physiological effects of a complex PAH mixture in an oil water-soluble fraction (WSF) have not been previously studied. This study is focused on the effects of WSF of oil on electrical activity and major ionic currents in the working myocardium of navaga (Eleginus nawaga), which is one of the most important commercial fish species in the Arctic. The authors found that 1 and 10% solutions of WSF of oil cause a marked increase in the duration of action potentials (APs) in navaga cardiomyocytes. This effect appears to be due to the suppression of rapid delayed rectifier current I_Kr (IC₅₀ approximately 3% in ventricular and atrial myocardium). At higher concentrations, WSF of oil also suppressed calcium current I_CaL (IC₅₀ = 10.6%), which led to a decrease in the contractile activity in isolated myocardial preparations. Unlike individual tricyclic PAHs, WSF of oil did not affect fast sodium current I_Na or AP upstroke velocity. An assessment of the content of tricyclic PAHs in 10% solution of WSF of oil showed that their total concentration is relatively low and does not exceed 100 nM. Thus, WSF of oil also has a powerful cardiotoxic effect in fish myocardium, but its effects differ from the previously studied effects of tricyclic PAHs and suggest the presence of yet unexplored oil compounds that have a more powerful toxic potential against ERG channels.