6533b832fe1ef96bd129a5e9

RESEARCH PRODUCT

Different metabolic behavior of long-chain n-3 polyunsaturated fatty acids in human platelets.

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Abstract Whereas numerous studies deal with the effects and metabolism of eicosapentaenoic acid (20:5( n −3)) in platelets, very few concern docosahexaenoic acid (22:6( n −3)), although both acids are consumed in equal amounts from most fish fat. The present paper reports the modulation of 22:6( n −3) oxygenation as well as that of endogenous arachidonic acid (20:4( n −6)) in 22:6( n −3)-rich platelets. Like the oxygenation of 20:5( n −3), the lipoxygenation of 22:6( n −3) occurred at a low level when incubated alone, but was markedly increased in the presence of 20:4( n −6), suggesting a similar peroxide tone dependency. 20:5( n −3) could not replace 20:4( n −6) in the increasing 22:6( n −3) lipoxygenation, whereas 22:6( n −3) shared the potentiating effect of 20:4( n −6) on both the cyclooxygenation and the lipoxygenation of 20:5( n −3). On the other hand, 20:5( n −3), 22:6( n −3) or 20:5( n −3) + 22:6( n −3) enrichment of platelet phospholipids inhibited the formation of cyclooxygenase but not lipoxygenase products from endogenous 20:4( n −6) in thrombin-stimulated platelets. In doing so, 22:6( n −3) appeared even more potent than 20:5( n −3), although it was not liberated after acylation in phospholipids, the opposite of what was observed with 20:5( n −3). Therefore, it seems that, in contrast to 20:5( n −3), which may compete with endogenous 20:4( n −6) at the cyclooxygenase level, 22:6( n −3) would affect the latter enzyme activity in a different way. We conclude that 20:5( n −3) and 22:6( n −3) behave differently and might act synergistically on the inhibition of platelet functions after fish fat intake.