Increasing DHA and EPA Concentrations Prolong Action Potential Durations and Reduce Transient Outward Potassium Currents in Rat Ventricular Myocytes

The goal of this study was to determine the mechanisms of n-3 polyunsaturated fatty acids (n-3 PUFA) on anti-arrhythmias and prevention of sudden death. The calcium-tolerant Sprague–Dawley rat ventricular myocytes were isolated by enzyme digestion. Effects of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on action potentials and transient outward potassium currents (Ito) of epicardial ventricular myocytes were investigated using whole-cell patch clamp techniques. Action potential durations (APDs) and Ito were observed in different concentrations of DHA and EPA. APD25, APD50, and APD90 with 0.1 μmol/L DHA and EPA were prolonged less than 15% and 10%. However, APDs were prolonged in concentration-dependent manners when DHA and EPA were more than 1 μmol/L. APD25, APD50, and APD90 were 7.7 ± 2.0, 21.2 ± 3.5, and 100.1 ± 9.8 ms respectively with 10 μmol/L DHA, and 7.2 ± 2.5, 12.8 ± 4.2, and 70.5 ± 10.7 ms respectively with 10 μmol/L EPA. Ito currents were gradually reduced with the increased concentrations of DHA and EPA from 1 to 100 μmol/L, and their half-inhibited concentrations were 2.3 ± 0.2 and 3.8 ± 0.6 μmol/L. The results showed APDs were prolonged and Ito current densities were gradually reduced with the increased concentrations of DHA and EPA. The anti-arrhythmia mechanisms of n-3 PUFA are complex, however, the effects of n-3 PUFA on action potentials and Ito may be one of the important mechanisms.