FISH-OIL PREPARATIONS RICH IN DOCOSAHEXAENOIC ACID MODIFY PLATELET RESPONSIVENESS TO PROSTAGLANDIN-ENDOPEROXIDE THROMBOXANE-A(2) RECEPTOR AGONISTS

The effects of daily dietary supplementation for 6 weeks with either 4 .5 g eicosapentaenoic acid (EPA) and 3.35 g docosahexaenoic acid (DHA) (group I, EPA/DHA = 1.33) or 3.5 g EPA and 6.4 g DHA (group II, EPA/D HA = 0.54) on platelet responsiveness to the stable prostaglandin (PG) endoperoxide analogue 9,11-dideoxy,9alpha-11alpha-methanoepoxy-PGF2alp ha (U46619) were studied in healthy volunteers. Dose-response curves ( DRC) of U46619-induced platelet aggregation were analysed by computeri zed non-linear curve fitting. In group I, the concentration of U46619 required for half-maximum platelet aggregation (EC50) remained unchang ed, whereas the Hill coefficient decreased from 6.2 to 3.3 (P < 0.02). In group II, characterized by a high intake of DHA, a considerable in crease of EC50 from 0.3 to 1.4 muM was found (P < 0.02). These results suggest different effects of EPA and DHA on the platelet thromboxane/ endoperoxide-amplifying system. The considerable shift of the DRC in g roup II suggests a direct effect of DHA on the presentation of the end operoxide receptor and/or post-receptoral events.