OBJECTIVETo investigate the effects of docosahexaenoic acid (DHA) on action potential (AP) and transient outward potassium current (I(to)) on ventricular myocytes of Sprague-Dawley rat.

METHODSCalcium-tolerant ventricular myocytes were isolated by enzyme digestion. The changes of AP and I(to) with increasing DHA at concentrations of 0, 10, 20, 40, 60, 80, 100, 120 and 200 micromol/L were recorded by whole-cell patch clamp configuration.

RESULTS(1) Action potential durations (APDs) were not affected by DHA at concentrations from 0 micromol/L to 30 micromol/L, while APDs were gradually prolonged in proportion with increasing DHA concentrations from 30 micromol/L to 200 micromol/L within 5 minutes and remained stable thereafter. APD(25), APD(50) and APD(75) were (7.7 +/- 2.0) ms, (21.2 +/- 3.5) ms, and (100.1 +/- 9.8) ms respectively at 100 micromol/L DHA. APD(25), APD(50), and APD(75) were (15.2 +/- 4.0) ms, (45.7 +/- 6.8) ms, and (215.6 +/- 15.7) ms respectively at 200 micromol/L DHA. (2) I(to) was gradually reduced with the increasing DHA concentrations from 10 micromol/L to 200 micromol/L. I(to) was blocked by DHA in a dose-dependent manner. I(to) current density was (30.1 +/- 7.2) pA/pF at DHA concentration of 60 micromol/L and its half-inhibition concentration was 58.3 micromol/L.

CONCLUSIONAPDs are gradually prolonged while I(to) reduced with increasing concentrations of DHA which might contribute to the anti-arrhythmia mechanisms of DHA.