Metabolism of asialoglycoproteins in cultured rat hepatocytes: evidence for receptor mediated uptake and degradation which is not feed-back regulated.

1. Cultured rat hepatocytes took up and degraded asialofetuin by a saturable mechanism. 2. The uptake was specific for desialylated fetuin; native fetuin and was taken up to a much lesser extent. 3. Degradation was inhibited by lysosomotropic agents; both uptake and degradation were, however, unaffected by cycloheximide. 4. The uptake was also unaffected by incubating the cells for 24 hr in the presence of large extracellular concentrations of unlabelled asialofetuin. 5. The data suggest that the asialoglycoprotein receptor is recycled and not subject to down-regulation.