Oral Administration Of Eicosapentanoic Acid (EPA) Stimulates Production Of Prostacyclin By Rat Aorta
Prostacyclin (PGI2) which is mainly produced in blood vessels has the most potent platelet antiaggregatory activity of any substance yet found. It is therefore thought that PGI2 is a preventive agent for cardiovascular diseases (CVD). We found that EPA orally administered to rats stimulated rat thoracic aorta to produce a PGl2like substance at 3 times normal levels. While there are several reports suggesting that EPA may contribute to the prevention of CVD by inhibiting platelet functions and improving plasma lipid concentrations, this is the first report that shows the relationships between orally administered EPA and PGl2~like substance production from aorta. METHODS: Two groups of Wistar rats were fed either a normal diet (group A) or a normal diet plus 74% pure EPA, 60 mg/kg/day (group B), for 8 weeks. Thoracic aortas were excised, cut into rings, and incubated in 50 mM Tris-HCl buffer, pH 7.5, for 10 min. The activity of the PGl2-like substance was measured by inhibition of human platelet aggregation. Platelet aggregability of rats in both groups was also checked with ADP as an aggregant. RESULTS: The rate of production of the PGl2~like substance by the aortas of group B was 4.0±1.4 ng/mg wet aorta/10 min (calibrated with authentic Na-PGI2), while that of group A was 1.4±0.5 (P<0.001). Platelet aggregability was depressed in group B rats. There was no significant difference in concentrations of plasma lipids such as total and HDL-cholesterol, triglycerides, and phospholipid. DISCUSSION: It has been suggested that EPA could prevent CVD through its antiaggregatory property. Now we suggest a new possibility that EPA could prevent CVD by stimulating blood vessels to produce more PGI2-like substance as well as by inhibiting platelet aggregation directly.