Uptake of palmitic acid by rabbit alveolar type II cells
- Univ. of Rochester School of Medicine, NY (USA)
Alveolar type II cells require a source of palmitic acid for synthesis of dipalmitoyl phosphatidylcholine (DPPC), a major constituent of pulmonary surfactant. Previous studies indicated that maximal rates of DPPC synthesis are achieved only if exogenous palmitate is available to the type II cell. Little is known of the mechanisms by which fatty acids enter type II cells. To determine if uptake is mediated by a membrane carrier system, as described in other cell types, we examined the kinetics of palmitate uptake. Using freshly isolated rabbit type II cells, we demonstrated that radiolabeled palmitate uptake was maximal and linear for 45 s; after 1 min the apparent rate of uptake declined. The initial uptake phase was taken as a measure of cellular fatty acid influx because intracellular radiolabeled palmitate remained 80% nonesterified at this time but was 55% esterified by 2 min. Cellular influx of palmitate showed saturation kinetics with increasing concentration of nonalbumin bound palmitate. Michaelis constant was 52.6 nM, and maximum velocity was 152 pmol.10(6) cells-1.min-1. The hypothesis that saturable cellular influx of palmitate is likely linked to the previously identified membrane fatty acid binding protein (MFABP) was supported by Western-blot analysis of rat lung tissue with an antibody to MFABP that demonstrated the presence of this carrier protein in lung tissue. These data suggest that palmitate uptake by type II cells is saturable and may be mediated by a membrane-associated carrier as described in other cell types.
- OSTI ID:
- 6325756
- Journal Information:
- American Journal of Physiology; (USA), Vol. 259:4 Pt 1; ISSN 0002-9513
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HEXADECANOIC ACID
MEMBRANE TRANSPORT
PHOSPHOLIPIDS
BIOSYNTHESIS
ANIMAL CELLS
CELL MEMBRANES
ESTERIFICATION
LUNGS
RADIOISOTOPES
TRACER TECHNIQUES
BODY
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
ESTERS
ISOTOPE APPLICATIONS
ISOTOPES
LIPIDS
MEMBRANES
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANS
RESPIRATORY SYSTEM
SYNTHESIS
550201* - Biochemistry- Tracer Techniques