Document Detail

Cholesterol flux between cells and high density lipoprotein. Lack of relationship to specific binding of the lipoprotein to the cell surface.
MedLine Citation:
PMID:  3040756     Owner:  NLM     Status:  MEDLINE    
The bidirectional flux of unesterified cholesterol between cells and high density lipoprotein (HDL) was studied in relationship to the binding of HDL to cells. At 100 micrograms at HDL protein/ml, the rate constant for cholesterol efflux from rat Fu5AH hepatoma cells is 3 X 10(-3)/min (t1/2 for efflux of 3.9 h), whereas efflux from GM3468 human fibroblasts is 0.075/4 h (equivalent to a t1/2 for efflux of 37 h). The relatively slow efflux of cholesterol from fibroblasts in comparison to rat hepatoma cells was observed previously with micellar and vesicular phospholipid-containing acceptors, which promote efflux by a mechanism involving the diffusion of cholesterol in the aqueous phase between the plasma membrane and the acceptor particles. When plotted against the logarithm of HDL concentration, the isotherms for efflux are centered at 300 and 100 micrograms of HDL protein/ml with the hepatoma cells and fibroblasts, respectively. These concentrations are 8-150 times greater than the corresponding values for Kd of specific HDL binding (2 and 12 micrograms of protein/ml, for hepatoma cells and fibroblasts, respectively). The treatment of HDL with tetranitromethane reduces the lipoprotein's affinity for specific cell-surface binding sites by 80-90%. However, at HDL concentrations of 5-60 micrograms of protein/ml, this treatment does not significantly inhibit cholesterol efflux from hepatoma cells, and inhibits efflux from fibroblasts an average of about 15%. Over the same range of concentrations, nitration alters influx by amounts less than 30% in the two cell types. These effects on flux do not parallel the reduced affinity of nitrated HDL for specific cell-surface binding sites. In summary, the present results do not support the concept that cholesterol transfer is facilitated by the specific cell-surface binding of HDL, but are consistent with the aqueous diffusion model of cholesterol transfer between cells and lipoproteins.
J B Karlin; W J Johnson; C R Benedict; G K Chacko; M C Phillips; G H Rothblat
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  262     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1987 Sep 
Date Detail:
Created Date:  1987-10-21     Completed Date:  1987-10-21     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  12557-64     Citation Subset:  IM    
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MeSH Terms
Carrier Proteins*
Cell Line
Cholesterol / metabolism*
Cholesterol, HDL / metabolism*
Fibroblasts / metabolism
Lipoproteins, HDL*
Liver Neoplasms, Experimental / pathology
Protein Binding
RNA-Binding Proteins*
Receptors, Cell Surface / metabolism*
Receptors, Lipoprotein*
Grant Support
Reg. No./Substance:
0/Carrier Proteins; 0/Cholesterol, HDL; 0/Lipoproteins, HDL; 0/RNA-Binding Proteins; 0/Receptors, Cell Surface; 0/Receptors, Lipoprotein; 0/high density lipoprotein receptors; 147605-06-9/high density lipoprotein binding protein; 57-88-5/Cholesterol

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