Lipid-free total parenteral nutrition and macrophage function in rats

Certain lipids are immunosuppressive when used for nutritional support, while other lipids and nutritional additives may enhance immunologic function. We hypothesized that total parenteral nutrition (TPN) may be immunosuppressive irrespective of lipids. Twenty-four rats underwent central vein catheterization and received either intravenous saline solution and oral chow or TPN alone. At 7 or 14 days, the animals were killed. Splenic and bone marrow macrophages were isolated and cultured in either M199 medium alone or were stimulated with Escherichia coli lipopolysaccharide. The supernatants were tested for prostaglandin E2 and C3. The splenic prostaglandin E2 levels were significantly higher in the TPN group following lipopolysaccharide stimulation at 7 days but not at 14 days. Administration of TPN to rats, even without lipids, may be immunosuppressive through the release of prostaglandin E2 from splenic macrophages following a septic challenge. This effect appears to be abolished after 14 days of TPN infusion.