Distribution of liposome-encapsulated iodixanol in rat liver cells

Distribution of liposome-encapsulated [(125)I]iodixanol in different types of liver cells following intravenous injection was studied in rats. The data showed that liposome-encapsulated [(125)I]iodixanol was rapidly taken up by the liver; after 15 min, radioactivity corresponding to nearly 25% of the injected radioactivity could be recovered therein. After 4 hr, approximately 60% of the injected radioactivity was in the liver. One week after injection, nearly 30% of the encapsulated radioactivity could still be recovered in the liver. Liposome-encapsulated [(125)I]iodixanol was taken up both by hepatocytes and the Kupffer cells. On a per cell basis, the uptake of liposome-encapsulated [(125)I]iodixanol in Kupffer cells was more than 10-fold greater than that in hepatocytes, while the contribution of liver endothelial cells to uptake was negligible. Osmotic protection studies showed that iodixanol does not readily diffuse across lysosomal membranes, indicating that loss of iodixanol from the liver probably occurred by recycling rather than by diffusion across phagolysosomal and plasma membranes.