MODIFICATION OF MONONUCLEAR CELL-FUNCTION AFTER INCUBATION WITH ALBUMIN-BOUND UNSATURATED FATTY-ACIDS OR SOYBEAN OIL EMULSION

Administration of total parenteral nutrition (TPN) with soybean oil em ulsion leads to a linoleic acid enrichment of the plasma membrane that may explain an tn vivo activation of mononuclear cells (MNC) seen in our previous studies. Fatty acids from the lipid emulsion may have bee n accessible to MNC after endocytosis of lipid particles, or by direct uptake of fatty acids after lipoprotein lipase hydrolyzation of the e mulsion triglycerides. To resemble the incorporation of fatty acids in vivo, we have modified MNC membrane lipid composition by incubation w ith different albumin-bound unsaturated fatty acids (UFA) or soybean o il emulsion. After incubation with albumin-bound linoleic and oleic ac id: the unstimulated release of superoxide anion was unchanged, while zymosan-stimulated release was 140% (n.s) and 112% (p<0.05) and phorbo l-myristate-acetate (PMA)-stimulated release 148% (p<0.05) and 124% (p <0.05) of controls, respectively. Incubation with other UFAs or emulsi on did not change superoxide anion release. Unstimulated lymphocyte pr oliferation increased 3 to 13-fold (p<0.05) after incubation with all UFAs compared to controls, while UFA incubation did not change phytohe magglutinin (PHA) or PMA-stimulated proliferation. Unstimulated lympho cyte proliferation was decreased after incubation with emulsion, while PHA/PMA-stimulated proliferation was unchanged. Increase in membrane fluidity was detectable only after incubation with emulsion. The incre ased reactivity may have been caused by changes in the lipid environme nt surrounding membrane-bound enzymes important for signal transductio n through the plasma membrane.