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 metabolism was investigated. Human peritoneal cells degraded low density lipoproteins (LDL) and acetylated LDL (acetyl-LDL) by saturable, high affinity receptor-mediated processes. Positive correlations of the percentage 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 significantly contributed to lipoprotein degradation. LDL receptor-mediated degradation was calcium dependent, and sensitive to pronase and chloroquine treatments. The receptor exhibited specificity for lipoproteins containing apolipoprotein B (apoB) or apolipoprotein E (apoE). Exposure of cells to LDL for 24 hrs significantly down-regulated LDL receptor-mediated degradation. Acetyl-LDL receptor-mediated degradation was calcium independent, inhibited by chloroquine, and was sensitive to pronase and fucoidin treatments. The scavenger receptor exhibited specificity for only acetyl-LDL. These results demonstrate that human peritoneal cells can provide a source of human tissue macrophages suitable for studies of cholesterol and lipoprotein metabolism and offer the opportunity for comparison of metabolic characteristics of in vivo maturated macrophages with available macrophage-like cell lines.