Tricyclic hydrocarbon fluorene attenuates ventricular ionic currents and pressure development in the navaga cod

Area of Science:

• Environmental toxicology
• Cardiovascular physiology
• Arctic marine biology

Background:

• Oil spills release polycyclic aromatic hydrocarbons (PAHs), posing significant risks to Arctic ecosystems.
• PAHs cause various toxic effects in fish, with cardiac dysfunction being a primary concern.
• Polar fish species like navaga cod are particularly vulnerable to environmental contaminants.

Purpose of the Study:

• To investigate the effects of fluorene, a common tricyclic PAH, on the cardiac electrophysiology and contractility of the polar navaga cod (Eleginus nawaga).
• To determine the sensitivity of major ionic currents (IKr, INa, ICaL, IK1) and action potential waveform to fluorene exposure.
• To assess the impact of fluorene on the overall contractile function of the isolated navaga cod heart.

Main Methods:

• Electrophysiological recordings of ionic currents (IKr, INa, ICaL, IK1) and action potentials in isolated ventricular myocytes.
• Assessment of contractile activity in isolated whole hearts subjected to varying fluorene concentrations.
• Pharmacological analysis including IC50 determination for fluorene's effect on IKr.

Main Results:

• Fluorene exhibited high sensitivity towards the rapid delayed rectifier K+ current (IKr), with an IC50 of 0.54 μM.
• Inward currents (INa and ICaL) showed moderate inhibition (20-28%) at 10 μM fluorene, while IKr was more potently affected.
• Action potential duration was prolonged by 3 μM fluorene, and AP upstroke velocity decreased at 10 μM; contractile function showed only modest depression.

Conclusions:

• Fluorene significantly impacts the electrical activity of the polar cod heart, primarily by affecting the IKr current.
• The observed electrophysiological disturbances suggest potential arrhythmogenic risks in Arctic fish exposed to fluorene.
• While electrical function is strongly affected, contractile activity is only moderately impacted, indicating a complex toxicological profile for this PAH in polar fish.