Uptake of liposomes and sheep red blood cells by the liver and spleen of rats with normal or decreased function of the reticuloendothelial system.

The distribution of negatively charged liposomes in rats with normal or depressed function of the liver RES was examined. RES activity was determined by the uptake of the sheep red blood cells (SRBC). Whereas pretreatment with colloidal carbon or dextran sulphate drastically diminishes the SRBC uptake by the liver, the liposome uptake is decreased by 12-15% only. In the spleen, such pretreatment boosts the SRBC uptake five- to sixfold, whereas liposome uptake was decreased by about 50%. This indicates that phagocytosis by the RES is only of several liposome-cell interactions. Consequently, the suppression of the RES function is of no practical use when attempting to suppress the preferential liposome uptake by the liver and spleen.