Mechanism of the hepatic lipase induced accumulation of high-density lipoprotein cholesterol by cells in culture

Journal Article · Tue Jul 02 04:00:00 EDT 1985 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00335a044· OSTI ID:6171220

Bamberger, M; Lund-Katz, S; Phillips, M C; Rothblat, G H

Hepatic lipase can enhance the delivery of high-density lipoprotein (HDL) cholesterol to cells by a process which does not involve apoprotein catabolism. The incorporation of HDL-free (unesterified) cholesterol, phospholipid, and cholesteryl ester by cells has been compared to establish the mechanism of this delivery process. Human HDL was reconstituted with /sup 3/H-free cholesterol and (/sup 14/C)sphingomyelin, treated with hepatic lipase in the presence of albumin to remove the products of lipolysis, reisolated, and then incubated with cultured rat hepatoma cells. Relative to control HDL, modification of HDL with hepatic lipase stimulated both the amount of HDL-free cholesterol taken up by the cell and the esterification of HDL-free cholesterol but did not affect the delivery of sphingomyelin. Experiments utilizing HDL reconstituted with /sup 14/C-free cholesterol and (/sup 3/H)cholesteryl oleoyl ether suggest that hepatic lipase enhances the incorporation of HDL-esterified cholesterol. However, the amount of free cholesterol delivered as a result of treatment with hepatic lipase was 4-fold that of esterified cholesterol. On the basis of HDL composition, the cellular incorporation of free cholesterol was about 10 times that which would occur by the uptake and degradation of intact particles. The preferential incorporation of HDL-free cholesterol did not require the presence of lysophosphatidylcholine. To correlate the events observed at the cellular level with alterations in lipoprotein structure, high-resolution, proton-decoupled /sup 13/C nuclear magnetic resonance spectroscopy (90.55 MHz) was performed on HDL3 in which the cholesterol molecules were replaced with (4-/sup 13/C)cholesterol by particle reconstitution.

• Research Organization: Medical College of Pennsylvania, Philadelphia
• OSTI ID: 6171220
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 14; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
BIOLOGICAL ACCUMULATION
CARBON 13
CARBON 14 COMPOUNDS
CARBON ISOTOPES
CARBOXYLESTERASES
CELL CULTURES
CHEMICAL REACTIONS
CHOLESTEROL
ENZYME ACTIVITY
ENZYMES
ESTERASES
ESTERIFICATION
EVEN-ODD NUCLEI
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPASE
LIPIDS
LIPOPROTEINS
LIVER CELLS
MAGNETIC RESONANCE
MAMMALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC COMPOUNDS
PROTEINS
RATS
RESONANCE
RODENTS
SOMATIC CELLS
STABLE ISOTOPES
STEROIDS
STEROLS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES