The aim of this report is to investigate the effect of eicosapentaenoic acid (EPA) on platelet aggregation (PA) and fatty acid composition of plasma and platelet phospholipid in rats compared to the non-EPA fed controls. Rats were fed a fish oil diet or a free EPA diet and the fish oil diet was composed of 6% of the total diet. In the case of the free EPA diet, 500mg of the free EPA diet was given per kilogram of body weight every day.
The concentration of EPA of the total fatty acids of the fish oil diet and the free EPA diet was 15% and 73% respectively.
We measured PA and fatty acid composition in rats 8 days after the feeding of the fish oil diet and 7 and 14 days after the feeding in the case of the free EPA diet. ADP- and collagen-induced PA were studied by the turbidometric method, and fatty acids were analysed by gas-liquid chromatography.
In the case of the feeding of the fish oil diet, collagen-induced PA was decreased significantly in the EPA fed rats compared to the controls (P<0.05). ADP-induced PA showed no significant difference between the two groups. Lipid analysis of plasma demonstrated that the ω3 acids, especially EPA, were increased significantly in the EPA fed rats compared to the controls and that the ω6 acids, especially arachidonic acid (AA), were decreased significantly. In the case of the feeding of the free EPA diet, collagen-induced PA was increased 7 days after the feeding, and decreased 14 days after the feeding compared to the controls, but the decrease was not significant. ADP-induced PA showed no significant difference between the two groups. Lipid analysis of platelet phospholipid demonstrated that EPA was increased in the EPA fed rats 7 and 14 days after the feeding compared to the controls, but AA was decreased significantly in the EPA fed rats only 14 days after the feeding.
These results show that after feeding of EPA, PA decreases and fatty acid composition of plasma and platelet changes, but the effect of EPA on PA and fatty acid composition may be influenced by the composition of total fatty acids of the diet and the duration of feeding.