Docosahexaenoic acid has influence on action potentials and transient outward potassium currents of ventricular myocytes

BACKGROUND: There are many reports about the anti-arrhythmic effects of ω-3 polyunsaturated fatty acids, however, the mechanisms are still not completely delineated. The purpose of this study was to investigate the characteristics of action potentials and transient outward potassium currents (I(to)) of Sprague-Dawley rat ventricular myocytes and the effects of docosahexaenoic acid (DHA) on action potentials and I(to). METHODS: The calcium-tolerant rat ventricular myocytes were isolated by enzyme digestion. Action potentials and I(to )of epicardial, mid-cardial and endocardial ventricular myocytes were recorded by whole-cell patch clamp technique. RESULTS: 1. Action potential durations (APDs) were prolonged from epicardial to endocardial ventricular myocytes (P < 0.05). 2. I(to )current densities were decreased from epicardial to endocardial ventricular myocytes, which were 59.50 ± 15.99 pA/pF, 29.15 ± 5.53 pA/pF, and 12.29 ± 3.62 pA/pF, respectively at +70 mV test potential (P < 0.05). 3. APDs were gradually prolonged with the increase of DHA concentrations from 1 μmol/L to 100 μmol/L, however, APDs changes were not significant as DHA concentrations were in the range of 0 μmol/L to 1 μmol/L. 4. I(to )currents were gradually reduced with the increase of DHA concentrations from 1 μmol/L to 100 μmol/L, and its half-inhibited concentration was 5.3 μmol/L. The results showed that there were regional differences in the distribution of action potentials and I(to )in rat epicardial, mid-cardial and endocardial ventricular myocytes. APDs were prolonged and I(to )current densities were gradually reduced with the increase of DHA concentrations. CONCLUSION: The anti-arrhythmia mechanisms of DHA are complex, however, the effects of DHA on action potentials and I(to )may be one of the important causes.