A comparison of the long-term effects of n-3 and n-6 polyunsaturated fatty acid dietary supplements and the action of indomethacin upon the mechanical performance and susceptibility of the rat heart to dysrhythmia.

The effect of different dietary lipid supplements on the contractility and susceptibility to isoprenaline-induced dysrhythmia in rat papillary muscles was examined after one year's prefeeding of either a low fat (4%, w/w) standard laboratory diet or those supplemented with additional (12%, w/w) saturated animal fatty acids (sheep perirenal fat; SF) or n-6 or n-3 polyunsaturated fatty acids (PUFA's) from sunflower seed oil (SSO) or tuna fish oil (FO) respectively. The positive inotropic response to Ca++ and the incidence of spontaneous tachyarrhythmias under isoprenaline load were significantly less in the muscles from SSO and FO fed animals compared to either mature REF or SF fed groups. Indomethacin reduced the response to Ca++ in both the REF and SF groups, but was without effect upon the muscles from SSO and FO groups. In addition this drug also significantly reduced isoprenaline-induced dysrhythmia in the muscles from REF and SF fed animals, but had no effect upon those from SSO and FO groups which were already less susceptible to dysrhythmia than the muscles from animals in the former two groups. These results indicate that "long-term" feeding of either n-3 or n-6 PUFA's can significantly reduce arrhythmogenesis in this species in vitro by mechanisms that may involve eicosanoid metabolism.