Chylomicron remnant-vitamin A metabolism by the human hepatoma cell line HepG2

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5620151

Lenich, C M

The binding and metabolism of (/sup 3/H) vitamin A-containing chylomicron remnants (CMR) by the human hepatoma cell line Hep G2 was studied. Mesenteric lymph chylomicrons (CM) were collected from (/sup 3/H) retinol-fed rats and incubated with lipoprotein-lipase to obtain CMR. At 4/sup 0/C, specific CMR binding was inhibited by excess unlabeled CMR. Specific binding predominated at low concentrations and approached saturation while total binding continued to increase over an extensive concentration range (0.45-32 ..mu..g triglyceride/ml). CMR uptake at 37/sup 0/C was greater than that of CM and at least 100 times more efficient than the fluid-phase pinocytosis of sucrose. CMR binding increased as the extent of lipolysis obtained by incubation with lipoprotein-lipase increased. Addition of human apolipoprotein E enhanced both CMR and CM binding. After internalization, Hep G2 cells hydrolyzed CMR-(/sup 3/H)retinyl esters and radiolabeled metabolites accumulated as a function of time and temperature. As a function of the concentration of (/sup 3/H) VA initially cell-bound, retinol and retinyl esters accumulated as the major cell-associated metabolites. By contrast, retinol was the major metabolite in the medium only at low VA concentrations as other more polar metabolites accumulated at higher concentrations (> 110 pmol VA/mg cell protein). The accumulation of CMR-VA metabolites in the medium was reduced when cells were preincubated in retinol-supplemented media. Also, the specific activity of retinol in the medium closely resembled that in the cell indicating that CMR-VA mixed with the cellular store prior to its secretion.

• Research Organization: Medical Coll. of Pennsylvania, Philadelphia (USA)
• OSTI ID: 5620151
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
BIOCHEMICAL REACTION KINETICS
CARBOXYLESTERASES
CARBOXYLIC ACID ESTERS
ENZYMES
ESTERASES
ESTERS
HYDROLASES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIPASE
LIVER CELLS
MAMMALS
MAN
METABOLISM
METABOLITES
ORGANIC COMPOUNDS
PRIMATES
RATS
REACTION KINETICS
RETINOIC ACID
RODENTS
SOMATIC CELLS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES
VITAMIN A
VITAMINS