In Vitro Binding and in Vivo Uptake of Chylomicron Remnants after their Hydrolysis by Hepatic Lipase
Chylomicron remnants (CM-RM), resulting from intravascular hydrolysis of chylomicrons by the endothelium bound lipoprotein lipases (LPL), are rapidly taken up by the liver. It appears clearly that this uptake is mostly receptor mediated1–3 and that CM-RM are taken up as whole particles. Hepatic lipase (HL), which exerts both a triacylglycerol lipase and phospholipase Al activity, may be involved in with CM-RM uptake. Indeed, its inhibition by a specific anti-HL antibody leads to an accumulation of apo B-48 rich-par ticles in the plasma of rats4,5. We have previously shown that CM-RM prealably hydrolyzed by HL and then added to isolated hepatocytes are taken up at a higher rate than non-treated remnants (6). Moreover, we showed that following hydrolysis by HL, there was no modification in remnant apo E levels (unpublished results). Since apo E is the ligand for remnant binding to their hepatic receptors1–3, we examined herein, whether HL-treatment of CM RM could despite unchanged apo E levels, increase 1) the binding of such particles to liver membranes and 2) their plasma clearance and hepatic uptake in vivo.
KeywordsCholesteryl Ester Hepatic Uptake Hepatic Lipase Liver Plasma Membrane Chylomicron Remnant
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