Journal of Lipid Research, Vol 31, 1241-1246, Copyright © 1990 by Lipid Research, Inc.
Trans n-3 eicosapentaenoic and docosahexaenoic acid isomers exhibit different inhibitory effects on arachidonic acid metabolism in human platelets compared to the respective cis fatty acids
SF O'Keefe, M Lagarde, A Grandgirard and JL Sebedio
INRA, Station de Recherches sur la Qualite des Aliments de l'Homme, Dijon, France.
N-3 trans geometrical isomers of 20:5 n-3 and 22:6 n-3 were isolated from
rats fed heated linseed oil. The ability of these acids to inhibit 20:4 n-6
metabolism by human platelets was examined. The concentrations required to
inhibit 50% of platelet aggregation (IC50) induced by 2.5 microM 20:4 n-6
were higher for the 20:5 delta 17t isomer compared to all cis 20:5 n-3;
means 29.2 and 7.6 microM, respectively (P less than 0.05). There were no
significant differences in IC50 between 22:6 delta 19t and all cis 22:6
n-3; means 4.3 and 5.6 microM, respectively (P greater than 0.05).
Inhibition of action of cyclooxygenase on 20:4 n-6 was similar for 20:5
delta 17t and 20:5 n-3 when examined at their IC50s, but comparison at
equal concentrations indicated that 20:5 n-3 was a significantly better
inhibitor (P less than 0.05). The ability to inhibit platelet aggregation
was paralleled by cyclooxygenase inhibition as determined by thromboxane B2
and 12- hydroxyheptadecatrienoic acid formation. 22:6 delta 19t appeared to
inhibit cyclooxygenase more completely than 22:6 n-3, examined at their
IC50s or at similar concentrations (P less than 0.05). Isomers of 20:5 n-3
and 22:6 n-3 having an n-3 cis or trans bond appear to have similar modes
of action, although levels required for effectiveness are different for the
C20 acids.
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