LIPOPROTEIN METABOLISM IN HUMAN PERITONEAL-CELLS

The feasibility of using human cells isolated from peritoneal dialysis effluent as a model for studying lipoprotein and cholesterol metaboli sm was investigated. Human peritoneal cells degraded low density lipop roteins (LDL) and acetylated LDL (acetyl-LDL) by saturable, high affin ity receptor-mediated processes. Positive correlations of the percenta ge of macrophage cells with degradation rates of LDL (r=0.742; p<0.05) and acetyl-LDL (r-0.931; p<0.01) indicated that macrophage cells sign ificantly contributed to lipoprotein degradation. LDL receptor-mediate d degradation was calcium dependent, and sensitive to pronase and chlo roquine treatments. The receptor exhibited specificity for lipoprotein s containing apolipoprotein B (apoB) or apolipoprotein E (apoE). Expos ure of cells to LDL for 24 hrs significantly down-regulated LDL recept or-mediated degradation. Acetyl-LDL receptor-mediated degradation was calcium independent, inhibited by chloroquine, and was sensitive to pr onase and fucoidin treatments. The scavenger receptor exhibited specif icity for only acetyl-LDL. These results demonstrate that human perito neal cells can provide a source of human tissue macrophages suitable f or studies of cholesterol and lipoprotein metabolism and offer the opp ortunity for comparison of metabolic characteristics of in vivo matura ted macrophages with available macrophage-like cell lines.