Chylomicron remnants bound to rabbit alveolar macrophages with high- affinity (K(d) = 3.3 ± 0.71 μg of protein/mL). The binding of chylomicron remnants was competitively inhibited in the presence of unlabeled remnants and to a lesser extent by unlabeled low-density lipoproteins. Pretreatment of cells with either trypsin or pronase inhibited degradation in a dose and time dependent manner, suggesting involvement of a cell surface protein. Chylomicron remnants were degraded by alveolar macrophages from Watanabe heritable hyperlipidemic (WHHL) rabbits, which are devoid of LDL receptor activity. Moreover, colchicine and monensin which are endocytotic and lysozomal inhibitors, respectively, did not have any effect on the degradation of chylomicron remnants by macrophages from normal rabbits. The absence of divalent cartons was found to enhance chylomicron remnant degradation by macrophages. Activated 0.2-macroglobulin and lactoferrin had no effect on chylomicron remnant degradation, indicating that the low- density lipoprotein receptor-related protein was not involved. In addition, the scavenger receptor inhibitors polyinosinic acid and fucoidan increased degradation of chylomicron remnant-ruling out uptake as a consequence of lipoprotein modification. Rather, the phagocytotic inhibitor cytochalasan D was found to significantly decrease chylomicron remnant degradation. Collectively, our data show that chylomicron remnants are metabolized by phagocytotic pathways initiated after binding to a cell surface protein which is distinct from the LDL receptor, LRP, or scavenger receptors.

Item Type:	Refereed Article
Research Division:	Chemical Sciences
Research Group:	Other Chemical Sciences
Research Field:	Chemical Sciences not elsewhere classified
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Chemical Sciences
Author:	Gennat, HC (Dr Hanni Gennat)
ID Code:	29590
Year Published:	1996
Web of Science® Times Cited:	34
Deposited By:	Menzies Centre
Deposited On:	2004-08-02
Last Modified:	2004-08-02
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