Influence of intravenous nutrients on bilirubin transport. II. Emulsified lipid solutions.

The effects of an emulsified intravenous fat preparation (Intralipid) on bilirubin transport were analyzed by cholestyramine extraction, spectrophotometric analysis, Sephadex gel filtration, peroxidase assay, bilirubin uptake by red blood cells, and by toxicity in tissue culture (L-929) cells. Intralipid is capable of binding bilirubin, but does not compete effectively with bilirubin bound to high affinity sites on albumin. The emulsified fat appears to have a higher affinity for bilirubin than for cell membranes. Red blood cells become coated with Intralipid, resulting in an increased association of bilirubin with the cell surface, but a decrease in pigment actually incorporated into the red cell membrane. In tissue culture experiments, Intralipid protected the cells from bilirubin toxicity. It is concluded that Intralipid may enhance the carrying capacity of serum for bilirubin, and thus exert a protective effect on tissues.