Effects of eicosapentaenoic acid on blood pressure, cell membrane fatty acids, and intracellular sodium concentration in essential hypertension

This study was designed to clarify the effects of orally administered eicos apentaenoic acid (EPA) on blood pressure, intracellular sodium content, and cell membrane fatty acid composition in patients with essential hypertensi on. After a 4-week run-in period, a study group of 17 male patients was ass igned to an 8-week treatment with EPA (2.7 g/day) or placebo in a randomize d, double-blind fashion with a crossover at week 4. Systolic blood pressure (SBP) was lower after treatment with EPA than after treatment with placebo (152.9 +/- 17.3 vs. 162.6 +/- 20.6 mmHg; p < 0.01), while diastolic blood pressure was not statistically different. Compared with the placebo treatme nt, EPA supplementation resulted in a decrease in intraerythrocyte sodium c ontent (R-Na; 11.17 +/- 0.63 vs. 10.44 +/- 1.28 nmol/l cells; p < 0.05) acc ompanied by an increase (p < 0.001) in erythrocyte membrane EPA content. Th e increase in membrane EPA content was related to the decrease in SBP (r = -0.52, p < 0.05) and the decrease in R-Na (r = -0.57, p < 0.02) during EPA treatment. The decrease in R-Na correlated positively with the decrease in SBP (r = 0.54, p < 0.05), and correlated negatively with the change in Na+- K+ ATPase activity (r = -0.59, p < 0.02). However, the change in Na+-K+ ATP ase activity did not directly correlate with the change in membrane EPA con tent. In conclusion, oral EPA supplementation increased membrane EPA conten t and reduced SBP in patients with essential hypertension. Based on the ass ociation between the increase in membrane EPA content and the decrease in i ntracellular sodium concentration, EPA may lower blood pressure by altering the activities of the membrane sodium transport systems.