Effect of dietary fish oils on the formation of leukotriene B4 and B5, thromboxane and platelet activating factor by rat leukocytes.

1. This study investigates the effect of dietary eicosapentaenoic acid (EPA), in the form of 'Max EPA' fish oil, on leukotriene B4 (LTB4) production in ionophore-stimulated rat leukocytes. Male Wistar rats (200-250 g) were fed for 3 weeks on a synthetic chow supplemented with either 10% by weight Max EPA oil or a coconut oil/safflower oil mixture. 2. The EPA-rich diet significantly increased the EPA content of leukocyte phospholipids and decreased the arachidonic acid level by 35% (P less than 0.001) compared with the control diet. 3. The concentration of leukotrienes in the ionophore (A23187) stimulated leukocytes was measured by reverse-phase HPLC using prostaglandin B2 as the internal standard. The EPA-supplemented diet caused a 50% decrease in LTB4 production (P less than 0.001) and a concomitant increase in the formation of the biologically less active LTB5 compared with the control diet. The amount of LTB4 and LTB5 produced by stimulated leukocytes closely resembled the changes in arachidonic acid and EPA content of leukocyte phospholipids. 4. Thromboxane B2 (TxB2) production in stimulated leukocytes from the EPA-fed animals was also decreased compared with the control group. 5. Although the formation of platelet activating factor by stimulated leukocytes was not altered by dietary treatment, the ability of an EPA-rich diet to decrease LTB4 and TxB2 production suggests that these diets may attenuate leukocyte activity and have useful anti-inflammatory effects.