Uptake of exogenous and endogenous eicosapentaenoic acid by cultured human mononuclear cells

Abstract

1. Peripheral blood mononuclear cells from eight healthy volunteers were cultured, with or without concanavalin A (Con A), in a medium containing (ml/1) 100 normal autologous serum, 100 experimental autologous serum or 100 heterologous (fetal calf) serum.2. The control and experimental autologous sera were obtained from the volunteers, before and after 15 d supplementation with 15 g fish oil (MaxEPA)/d to provide 1.5 g eicosapentaenoic acid (EPA; 20:5n-3)/d. The sera were frozen at -20°. The level of EPA increased from trace quantities in the control autologous serum to 14.3% w/w free fatty acids and between 6.9 and 8.1% w/w lipoprotein phospholipids in the experimental autologous serum. The heterologous fetal calf serum was enriched with EPA, complexed with bovine serum albumin, to provide a final concentration of 15μg/ml. All culture medium contained 10 ml fresh autologous serum/l and cells were obtained from the volunteers for the culture studies about 60 d after the end of EPA supplementation.3. Portions of cells were removed from culture at 36, 48 and 72 h for phospholipid fatty acid analysis.4. The level of EPA in phospholipids of cells cultured with exogenous EPA in fetal calf serum was increased significantly (P< 0.05) at all sampling times, both with and without Con A. By 48 h the levels had peaked at 15.8 (se2.7) and 18.4 (se4.5) % w/w respectively.5. Resting cells, i.e. with no Con A present, failed to accumulate EPA when cultured in the experimental autologous serum containing 8.6% w/w total lipids as endogenous EPA. When cells were stimulated to divide by the mitogen Con A, there was a gradual increase in phospholipid EPA levels of mononuclear cells cultured with experimental autologous serum containing endogenous EPA. The maximum level obtained was at 72 h (7.2 (se2.7)).6. In a separate experiment, the effect of Con A at increasing doses (0, 1,5, 10 and 20 μg, final concentration) on lymphocyte blastogenesis was determined by estimating the incorporation of3[H]thymidine. No significant effects due to serum in the culture medium were observed.