Effects of the incubation of long-chain polyunsaturated fatty acids on platelet lipids and thromboxane release

Alterations of dietary lipids have been advocated to manipulate platelet release of thromboxane A₂. We studied the effects of incubating platelets with several different polyunsaturated fatty acids on platelet-lipid profile and release of thromboxane A₂ in response to platelet stimulation. Porcine platelets were isolated by centrifugation, washed three times in Tyrode's solution, and incubated with fatty acids (500 μM) in Tyrode's solution with albumin. Seven polyunsaturated fatty acids of varying lengths (18-, 20-, and 22-carbon chain) of the ω3 and ω6 families were incubated for 60 min at concentrations of 0, 10, 30, and 100 μM with saturated fatty acids comprising the remainder of the 500 μM fatty acids, The platelets were then stimulated for 5 min with A₂₃₁₈₇ (30 μM). Indomethacin was added, and the platelets were pelleted. Platelet lipids were extracted in hexane, transesterified and quantified by gas chromatography. Using radioimmunoassay, we measured thromboxane B₂, the stable metabolite of thromboxane A₂, in the platelets' supernatant. A 1-h incubation in each of the seven polyunsaturated fatty acids had no significant effect on platelet-lipid composition. We found a significant increase in thromboxane B₂ production in arachidonic acid (100 μM) incubated platelets (324.0 ± 63.8% of baseline) that was inhibited by eicosapentaenoic acid (81.0 ± 26.8%, P < 0.01) and to a lesser extent by dihomogammalinolenic acid (189.8 ± 28.3%, P < 0.03). We conclude that in altering diets to affect platelet release of thromboxane, the two fatty acids of interest are the 20-carbon chain fatty acids, dihomogammalinolenic acid and eicosapentaenoic acid. The ideal amount of each of these fatty acids to be incorporated entails supraphysiologic but pharmacologically achievable levels of fatty acids in plasma.