INCREASED DIETARY ARACHIDONIC-ACID ENHANCES THE SYNTHESIS OF VASOACTIVE EICOSANOIDS IN HUMANS

Data on the effect of dietary arachidonic acid (AA) (20:4n-6) on the s ynthesis of thromboxane and prostacyclin (PGl(2)) in humans are lackin g. We measured the effect of 1.5 g/d (ca. 0.5 en%) of 20:40-6 added is ocalorically to a stabilization (low-AA) diet on the excretion of 11-d ehydrothromboxane B-2 (11-DTXB2) and 2,3-dinor-6-oxo-PGF(1 alpha) (PGl (2)-M). In a crossover design, 10 healthy men, living in a metabolic u nit, were fed a diet (low-AA) containing 210 mg/d of 20:4n-6 for 65 d and an identical diet (high-AA) that contained 1.5 g/d of additional 2 0:4n-6 for 50 d. Three-day urine pools were collected at the end of ea ch dietary period and analyzed for eicosanoids by gas chromatography-e lectron capture negative ion-tandem mass spectrometry. Mean excretion of 11-dehydrothromboxane B-2 was 515 +/- 76, 493 +/- 154, and 696 +/- 144 ng/d (SD; n = 10) during the acclimation (15 d) low-AA diet and hi gh-AA diet periods, respectively (41% increase from low-AA to high-AA diet, P = 0.0037); mean excretion of PGl(2)-M was 125 +/- 40, 151 +/- 36, and 192 +/- 55 ng/d (SD; n = 10) during acclimation (15 d) low-AA and high-AA diets, respectively (27% increase from low-AA to high-AA d iets; P = 0.0143). Thus, both the metabolites of thromboxane and PGl(2 ), increase on the high-AA diet. Furthermore, both indicated changes i n metabolite excretion may be associated with measurable effects on se veral physiologically significant cellular functions, such as platelet aggregation in vivo and inflammation in response to immune challenges .