High‐affinity association and degradation of 125I‐labelled low density lipoproteins by human hepatocytes in primary culture

Catabolism of homologous low density lipoproteins (LDL) was studied in primary culture of human hepatocytes (HH). The cell association and degradation of 125I-labeled LDL (125I-LDL) were curvilinear functions of substrate concentration. Cell association and degradation of 125I-LDL were inhibited by excess unlabeled LDL. Reductive methylation of unlabeled LDL abolished its ability to complete with 125I-LDL for cell association and degradation. Preincubation of HH with unlabeled LDL caused a 63% inhibition of the 125I-LDL degradation. It is concluded that the catabolism of LDL by HH proceeds in part through a receptor-mediated pathway similar to that demonstrated on extrahepatic cells.