Specific incorporation of asialofetuin‐labeled liposomes into hepatocytes through the action of galactose‐binding protein

Asialofetuin‐labelled liposomes (AF‐liposomes) having mean diameters of 0.13 μm ([S]) and 0.35 μm ([L]) were obtained by the subsequent extrusion method in combination with dialysis. Intravenously administered AF‐liposomes [S] were rapidly cleared from the systemic circulation. By pre‐ and post‐treatment of the rats with free asialofetuin (AF), the rate of elimination decreased to that of non‐labelled liposomes (N‐liposomes) [S]. The liver uptake of AF‐liposomes [S] (60 per cent of dose in 30 min) was about twice that of N‐liposomes [S]. Forty‐seven per cent of the AF‐liposomes [S] incorporated into the liver were found in the parenchymal cell fraction as against 20 per cent in the non‐parenchymal cell fraction. In contrast, N‐liposomes [S] were taken up primarily by non‐parenchymal cells as was also the case for AF‐ or N‐liposomes [L]. Both the lipid and aqueous markers of AF‐liposomes [S] were detected in subcellular fractions of the liver, but their distribution was noted to change differently with the lapse of time. Intravenously administered AF‐liposomes [S] were specifically recognized by galactose‐binding protein and underwent disruption in the cell after being taken up by hepatocytes. AF‐liposomes [S] may possibly be utilized to deliver drugs into hepatocytes.