Liver endothelium binds, transports, and desialates ceruloplasmin which is then recognized by galactosyl receptors of hepatocytes.

Incubation of 125I-labeled ceruloplasmin with various fractions of liver cell suspensions at 4 degrees C led to its exclusive binding to the endothelium. At 37 degrees C the uptake was followed by internalization and subsequent release of the labeled molecule which, then, had acquired the capacity to bind to the hepatocytes. Unlabeled CP did not inhibit this hepatocyte binding, but two galactose-containing molecules, asialofetuin and asialoceruloplasmin, did. Incubation of double-labeled CP (sialic acid with 3H, protein with 125I) with endothelial cells led to the dissociation of two labels, indicating desialation of CP. The findings indicate that liver endothelium takes up and desialates CP which is subsequently released and recognized by hepatocytes through their membrane galactosyl receptors. This work offers a physiological function for the galactosyl receptors on hepatocyte membrane.