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Accumulating evidence has suggested that ω3-polyunsaturated fatty acids (ω3-PUFAs) may have beneficial effects in the prevention/treatment of cardiovascular diseases, while controversies still remain regarding their anti-arrhythmic potential. It is not clear yet whether ω-3-PUFAs can suppress early afterdepolarizations (EADs) induced by oxidative stress. In the present study, we recorded action potentials using the patch-clamp technique in ventricular myocytes isolated from rabbit hearts. The treatment of myocytes with H 2 O 2  (200 μM) prolonged AP durations and induced EADs, which were significantly suppressed by docosahexaenoic acid (DHA, 10 or 25 μM;  n  = 8). To reveal the ionic mechanisms, we examined the effects of DHA on L-type calcium currents ( I  Ca.L ), late sodium ( I  Na ), and transient outward potassium currents ( I  to ) in ventricular myocytes pretreated with H 2 O 2 . H 2 O 2  (200 μM) increased  I  Ca.L  by 46.4% from control (−8.4 ± 1.4 pA/pF) to a peak level (−12.3 ± 1.8 pA/pF,  n  = 6,  p  < 0.01) after 6 min of H 2 O 2  perfusion. H 2 O 2 -enhanced  I  Ca.L  was significantly reduced by DHA (25 μM; −7.1 ± 0.9 pA/pF,  n  = 6,  p  < 0.01). Similarly, H 2 O 2 -increased the late  I  Na  (−3.2 ± 0.3 pC) from control level (−0.7 ± 0.1 pC). DHA (25 μM) completely reversed the H 2 O 2 -induced increase in late  I  Na  (to −0.8 ± 0.2 pC,  n  = 5). H 2 O 2  also increased the peak amplitude of and the steady state  I  to  from 8.9 ± 1.0 and 2.16 ± 0.25 pA/pF to 12.8 ± 1.21 and 3.13 ± 0.47 pA/pF respectively ( n  = 6,  p  < 0.01, however, treatment with DHA (25 μM) did not produce significant effects on current amplitudes and dynamics of  I  to  altered by H 2 O 2 . In addition, DHA (25 μM) did not affect the increase of intracellular reactive oxygen species (ROS) levels induced by H 2 O 2  in rabbit ventricular myocytes. These findings demonstrate that DHA suppresses exogenous H 2 O 2 -induced EADs mainly by modulating membrane ion channel functions, while its direct effect on ROS may play a less prominent role.

Docosahexaenoic Acid Reduces the Incidence of Early Afterdepolarizations Caused by Oxidative Stress in Rabbit Ventricular Myocytes