"In vivo" distribution of liposomes between parenchymal and non parenchymal cells in rat liver.

The in vivo uptake of 3H-methotrexate containing, 14C-cholesterol labelled liposomes was determined for the two major liver cell populations, parenchymal cells (PC) and non-parenchymal cells (NPC) after intravenous injection of the liposomes into normal rats and rats with a portocaval shunt, followed by isolation and purification of the two cell types. One hour after injection, the purified NPC had bound 2-3 times more of the liposome-attached radioactivity per cell than the purified PC, whereas 6 hours after injection the ratio was inverted. In animals with a portocaval shunt, the PC contained 3-4 times more liposomal radioactivity per cell than NPC already 1 hour after injection, although the total uptake by the whole liver was not diminished under these conditions. Recalculating the data obtained from the isolated cells for the whole liver, it is found that 1 hour after injection the liver NPC had bound the same amount of liposomal radioactivity as liver PC, although they account for only 7% of the liver volume. After 6 hours, the PC had bound 5 times more liposomal radioactivity than the NPC; this ratio is achieved in animals with a portocaval shunt already 1 hour after injection. This shift is simultaneously caused by a gain of PC-bound radioactivity and decrease of NPC-bound radioactivity.