Effects of dietary 9-trans, 12-trans linoleate on arachidonic acid metabolism in rat platelets.

In order to determine the minimal amount of dietary 9-trans, 12-trans-linoleate which can decrease endoperoxide metabolites synthesized and their precursor in rat platelets, graded amounts (0, 0.1, 0.5, 1.0, 2.5%) of the trans-linoleate were fed to rats with a constant amount of all-cis-linoleate (2.5%) for 12 weeks. Arachidonic acid levels in platelet phospholipids of groups receiving the trans-linoleate at 2.5 and 1.0% were significantly (p less than 0.01) lower than that of the control receiving no trans-linoleate. Concentrations of TXB2 and PGF2 alpha in sera of the group receiving 2.5% trans-linoleate were significantly (p less than 0.05) lower than those of the control; however, there was no difference between the group receiving 1.0% trans-linoleate and the control. To determine whether the difference in serum concentration of endoperoxide metabolites could be manifested if rats were fed for longer period of time, 2 groups of rats were again fed diets containing 0 and 1.0% trans-linoleate, respectively, for 16 weeks. Arachidonic acid in platelet phospholipids of the group receiving the trans-linoleate was again significantly (p less than 0.01) lower than that of the control group. Concentrations of TXB2 and PGF2 alpha, and 12-hydroxyeicosatetraenoic acid formed in platelets, were smaller in the group receiving trans-linoleate than the control group; however, the difference was not statistically significant. These results indicated that all-trans-linoleate can reduce arachidonic acid metabolites formed in rat platelets when its dietary level is equal to or exceeds the level of all-cis-linoleate.