Beyond Acute Toxicity: Subchronic PAH Effects on Navaga Cod Ventricular Cardiomyocytes

ABSTRACT This dataset contains the original, unprocessed electrophysiological recordings underlying the study "Beyond Acute Toxicity: Subchronic PAH Effects on Navaga Cod Ventricular Cardiomyocytes". The data are provided as Axon Binary Format (.abf) files generated during whole-cell patch-clamp experiments on isolated ventricular cardiomyocytes of the navaga cod (Eleginus nawaga), an Arctic gadid fish. The experiments examined how prolonged (5–8 h) incubation with the water-soluble fraction (WSF) of crude oil (10%), phenanthrene (3 µM), or 3-methylphenanthrene (3 µM) alters cardiac electrical activity, relative to untreated controls. Ventricular myocytes were enzymatically isolated, and cells from each fish were distributed across the control and treatment groups. For each condition the recordings include current-clamp measurements of action potentials and voltage-clamp measurements of the fast sodium current (INa), the rapid delayed rectifier potassium current (IKr), the inward rectifier potassium current (IK1), and the L-type calcium current (ICa,L). All recordings were acquired with an Axopatch 200A amplifier at the White Sea Biological Station of Lomonosov Moscow State University (summer 2025). The .abf files can be opened with Clampfit (Molecular Devices) or open-source tools such as Stimfit or the pyABF Python library, and constitute the raw source data for all action-potential parameters and ionic current densities reported in the associated article. METHODS Animals and ethics. Experiments were performed at the White Sea Biological Station of Lomonosov Moscow State University (Karelia, Russia). Adult navaga cod (Eleginus nawaga) of either sex (body mass 96.4 ± 7.42 g; N = 21) were caught by hook and line in Kandalaksha Bay of the White Sea in mid-summer (July 2025; water temperature 10–14 °C) and held in flow-through seawater aquaria. All procedures were approved by the MSU Bioethics Commission (research application 164-a and animal-holding application 13.2, Commission meeting 156-d, 16.11.2023). Fish were euthanised by a sharp blow to the head followed by destruction of the brain (EU Directive 2010/63/EU, Annex IV), with death confirmed by cessation of opercular movement. Cardiomyocyte isolation. Ventricular myocytes were obtained by enzymatic dissociation. The heart was rapidly excised, the bulbus arteriosus was cannulated, and the heart was perfused retrogradely with a nominally Ca²⁺-free isolation solution containing (in mmol L⁻¹): NaCl 100, KCl 10, KH₂PO₄·2H₂O 1.2, MgSO₄·7H₂O 4, taurine 50, glucose 10, HEPES 10 (pH 6.9), supplemented with collagenase type IA (0.35 mg mL⁻¹), trypsin type IX (0.15 mg mL⁻¹), and fatty-acid-free bovine serum albumin (0.35 mg mL⁻¹). After 7–15 min of perfusion the ventricle was excised, minced, and gently triturated to release single myocytes, which were stored in the isolation solution at 4 °C for up to 8 h. Experimental design and incubation. A within-animal design was used: myocytes isolated from each fish were divided into three to four aliquots, randomly assigned to a control group and to treatment groups, so that cells from every individual contributed to several groups and control and treated cells were drawn from the same isolation and recorded on the same day in interleaved order. Aliquots were incubated for 5–8 h before recording with one of the following: 10% water-soluble fraction (WSF) of Urals-grade crude oil, 3 µM phenanthrene (Phe), or 3 µM 3-methylphenanthrene (3-MP). Stock solutions of Phe and 3-MP (10⁻² M in DMSO) were renewed every two days. The WSF was prepared fresh daily by agitating 50 µL of crude oil in 50 mL of isolation solution for 5 min, allowing the mixture to settle in a separating funnel, and collecting the lower aqueous phase free of visible oil droplets. Patch-clamp recordings. Ionic currents and action potentials were recorded in the whole-cell configuration with an Axopatch 200A amplifier and WinWCP v.5.7.7 software, using borosilicate pipettes of 2.0–3.0 MΩ. Cells were superfused (~1.5 mL min⁻¹) at 12 °C. The recordings stored in this dataset correspond to the following configurations: Action potentials (current-clamp). External K⁺-based saline (in mmol L⁻¹): NaCl 150, KCl 3.5, NaH₂PO₄ 0.4, MgSO₄ 1.5, CaCl₂ 1.8, glucose 10, HEPES 10 (pH 7.3); K⁺-based pipette solution: KCl 140, MgCl₂ 1, EGTA 5, MgATP 4, Na₂GTP 0.3, HEPES 10 (pH 7.2). Only cells with a stable resting membrane potential more negative than −70 mV were used; APs were evoked by 1 ms pulses at 0.2 Hz. Rapid delayed rectifier K⁺ current (IKr). Double-pulse protocol from a holding potential of −80 mV (2 s step to between −80 and +60 mV in 20 mV increments, followed by a 2 s step to −20 mV); IKr quantified as the tail current at −20 mV and isolated by subtraction of recordings in 2 µM E-4031. Nifedipine (20 µM) was present to block ICa,L. Inward rectifier K⁺ current (IK1). 1 s voltage ramp from +60 to −120 mV applied every 10 s from −80 mV; IK1 defined as the Ba²⁺-sensitive component (subtraction of recordings in 2 mM BaCl₂). Fast Na⁺ current (INa). Reduced-Na⁺ external solution (in mmol L⁻¹): NaCl 20, CsCl 120, MgCl₂ 1, CaCl₂ 0.5, glucose 10, HEPES 10 (pH 7.7); pipette solution: NaCl 5, CsCl 130, MgCl₂ 1, EGTA 5, Mg₂ATP 5, HEPES 5 (pH 7.2), with nifedipine (20 µM) and ~60% series-resistance compensation. A two-step protocol (300 ms steps from −120 to +60 mV in 10 mV increments, then a 200 ms test pulse to −20 mV) was used to obtain the current–voltage relationship and the steady-state activation and inactivation. L-type Ca²⁺ current (ICa,L). K⁺ replaced by equimolar Cs⁺; pipette solution (in mmol L⁻¹): CsCl 130, MgCl₂ 1, EGTA 5, tetraethylammonium chloride 15, MgATP 4, Na₂GTP 0.3, HEPES 10 (pH 7.2). 250 ms steps from a holding potential of −40 mV (to inactivate INa) to between −40 and +50 mV in 10 mV increments.