Comparison of the Rate of Uptake and Biologic Effects of Retinol Added to Human Keratinocytes Either Directly to the Culture Medium or Bound to Serum Retinol-Binding Protein

Retinol circulates in the plasma bound to retinol-binding protein (RBP), but the mechanism by which retinol is transferred from RBP to target cells is not known. To study retinol delivery, human keratinocytes (HKc) were incubated with [3H]retinol added directly to the culture medium or bound to RBP...

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Bibliographic Details
Published in:Journal of investigative dermatology 1991-08, Vol.97 (2), p.298-304
Main Authors: Hodam, John R, Hilaire, Phaedria St, Creek, Kim E
Format: Article
Language:English
Subjects:
550501 - Metabolism- Tracer Techniques
560300 - Chemicals Metabolism & Toxicology
ANIMAL CELLS
ANIMAL TISSUES
ANIMALS
BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
Biological and medical sciences
BIOLOGICAL EFFECTS
BODY
CARBON-CARBON LYASES
CARBOXY-LYASES
CARBOXYLIC ACID ESTERS
CARCINOGENS
CELL CULTURES
Cells, Cultured
COMPARATIVE EVALUATIONS
CULTURE MEDIA
DAYS LIVING RADIOISOTOPES
DECARBOXYLASES
DOSE-RESPONSE RELATIONSHIPS
ELECTRON CAPTURE RADIOISOTOPES
ENZYME ACTIVITY
ENZYMES
EPIDERMIS
EPITHELIUM
ESTERS
EVALUATION
General and cellular metabolism. Vitamins
Humans
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
Keratinocytes - cytology
Keratinocytes - metabolism
KINETICS
LYASES
MAMMALS
MAN
Medical sciences
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
Pharmacology. Drug treatments
PHORBOL ESTERS
PRIMATES
PROTEINS
RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT
RADIOISOTOPES
REACTION KINETICS
RETINOIC ACID
Retinol-Binding Proteins - metabolism
Retinol-Binding Proteins, Plasma
SKIN
TISSUES
TRACER TECHNIQUES
Tritium
TRITIUM COMPOUNDS
UPTAKE
VERTEBRATES
VITAMIN A
Vitamin A - pharmacokinetics
Vitamin A - pharmacology
VITAMINS
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Description
Summary:Retinol circulates in the plasma bound to retinol-binding protein (RBP), but the mechanism by which retinol is transferred from RBP to target cells is not known. To study retinol delivery, human keratinocytes (HKc) were incubated with [3H]retinol added directly to the culture medium or bound to RBP and the uptake of [3H]retinol was determined at various times. During the first hour of incubation, the rate of [3H]retinol accumulation by HKc was about 40 times greater when the vitamin was added directly to the media rather than bound to RBP. Although maximal uptake of [3H]retinol added directly to the culture medium occurred at 3 h, the uptake of [3H]retinol from RBP was linear with time for at least 72h. By 57 h, cell-associated [3H]retinol was the same whether it was added directly to the culture medium or bound to RBP. Excess unlabeled retinol or pretreatment of HKc with retinol had no effect on the uptake of [3H]retinol added directly to the culture medium or bound to RBP. Apobut not holo-RBP was capable of competing with HKc for the uptake of [3H]retinol from RBP. No specific or saturable binding of 125I-labeled RBP to HKc cultured in the absence or the presence of retinol was found. The dose response of retinol inhibition of cholesterol sulfate synthesis and phorbol ester-induced ornithine decarboxylase activity or retinol modulation of keratin expression was the same whether the retinol was delivered to HKc bound to RBP or added directly to the medium. Our data support a mechanism for retinol delivery from REP to HKc that does not involve cell-surface RBP receptors but instead suggest that the vitamin is first slowly released from RBP and then becomes cell-associated from the aqueous phase. This mechanism is consistent with the finding that HKc respond identically to retinol whether or not it is delivered to them bound to RBP.
ISSN:0022-202X
1523-1747
DOI:10.1111/1523-1747.ep12480562