Termination of asynchronous contractile activity in rat atrial myocytes by n-3 polyunsaturated fatty acids

A protective effect of the n-3 polyunsaturated fatty acids (PUFAs) in preventing ventricular fibrillation in experimental animals and cultured cardiomyocytes has been demonstrated in a number of studies. In this study, a possible role for the n-3 PUFAs in the treatment of atrial fibrillation (AF) was investigated at the cellular level using atrial myocytes isolated from young adult rats as the experimental model. Electrically-stimulated, synchronously-contracting myocytes were induced to contract asynchronously by the addition of 10 mu M isoproterenol. Asynchronous contractile activity was reduced following acute addition of the n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) at 10 mu M, compared with no fatty acid addition (from 99.0 +/- 1.0% to 30.7 +/- 5.2% (p < 0.05) for DHA and 23.8 +/- 2.8% (p < 0.01) for EPA), while the saturated fatty acid, docosanoic acid (DA) and the methyl ester of DHA (DHA m.e.) did not exert a significant effect on asynchronous contractile activity. Asynchronous contractile activity was also reduced to 1.7 +/- 1.7% in the presence of the membrane fluidising agent, benzyl alcohol (p < 0.001 vs no fatty acid addition). Cell membrane fluidity was determined by steady state fluorescence anisotropy using the fluorescent probe, TMAP-DPH. Addition of DHA, EPA or benzyl alcohol significantly increased sarcolemmal membrane fluidity (decreased anisotropy, r(ss)) of atrial myocytes compared with no addition of fatty acid (control) (from r(ss) = 0.203 +/- 0.004 to 0.159 +/- 0.004 (p < 0.01) for DHA, 0.166 +/- 0.001 (p < 0.01) for EPA and 0.186 +/- 0.003 (p < 0.05) for benzyl alcohol, while DA and DHA m.e, were without effect, It is concluded that the n-3 PUFAs exert anti-asynchronous effects in rat atrial myocytes by a mechanism which may involve changes in membrane fluidity.