[Study of VLDL- and HDL-receptor on isolated parenchymal and non-parenchymal cells from rat liver].

Saturable high-affinity VLDL and HDL receptor on parenchymal cells (PC), and non-parenchymal cells (NPC) freshly isolated from rat liver were studied. The VLDL- and HDL-receptor could mediate liver PC and NPC to bind, uptake, and degrade 125I-labeled human VLDL and apoE-deficient HDL3, and the activities of these two receptors (expressed as ng/mg cell protein) on NPC were about 10- and 4-fold higher than those on PC, respectively. VLDL receptor on NPC with kd 15.0-34.2 micrograms/ml and Bmax 2170-2607 ng/mg cell protein could be inhibited by EDTA, and down-regulated by cell cholesterol content. HDL receptor on NPC with kd 10.1-17.7 micrograms/ml and Bmax 1004-2738 ng/mg cell protein could not be inhibited by EDTA, but could be up-regulated by cell cholesterol content. Competitive inhibition assay showed that VLDL receptor could not only bind VLDL and LDL, but also bind HDL3 to some extent. Unlabeled purified apolipoprotein CIII-1, but apoAI, CI, CII, could effectively inhibit 125I-labeled VLDL binding to NPC. These results suggest that liver NPC may be more active than PC in clearing VLDL and HDL from circulation, and apolipoprotein CIII play an important inhibitory role in these receptor-mediated processes.