Interaction of human lactoferrin with the rat liver
Binding of human lactoferrin (hLf) by purified rat liver plasma membranes was studied to clarify whether the liver possesses specific hLf receptors. The binding was rapid between 4 degrees and 37 degrees C, with a pH optimum close to 5.0. At 22 degrees C and in glycine-NaOH (5 mM, pH 7.4) containing 150 mM NaCl and 0.5% albumin, 1 microgram of membrane bound a maximum of 11.8 ng hLf. The dissociation constant of the interaction was 1.6 X 10(-7) M. Other proteins of high isoelectric points (lactoperoxidase, lysozyme, and particularly salmine sulfate) and a piperazine derivative inhibited hLf binding in a concentration- dependent manner. In contrast, monosaccharides (galactose, N- acetylgalactosamine, mannose, and fucose) were ineffective. By omitting NaCl from the incubation buffer, binding was increased 3.6-fold. Erythrocyte ghosts bound hLf less firmly and alveolar macrophages more firmly than hepatic plasma membranes. Liver cell fractionations performed after the intravenous injection of labeled hLf showed that approximately 88% of the hepatic radioligand was associated with parenchymal cells. When binding was expressed per unit of cell volume, however, more hLf was present in nonparenchymal than in parenchymal cells, implying that the above value was determined by the relative cell masses rather than affinities alone. It is concluded that the binding of hLf by hepatic plasma membranes is electrostatic, i.e., is mediated by the cationic nature of the ligand, and that it is explicable in terms of a ''specific nonreceptor interaction'' of the generalized type proposed by Cuatrecasas and Hollenberg.
- Research Organization:
- McMaster Univ. Health Sciences Centre, Hamilton, Ontario, Canada
- OSTI ID:
- 5681880
- Journal Information:
- Am. J. Physiol.; (United States), Vol. 248
- Country of Publication:
- United States
- Language:
- English
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LACTOFERRIN
CHEMICAL BONDS
RECEPTORS
AFFINITY
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL HALF-LIFE
CELL MEMBRANES
LIGANDS
LIVER
MACROPHAGES
MONOSACCHARIDES
PROTEINS
RATS
SODIUM CHLORIDES
ALKALI METAL COMPOUNDS
ANIMAL CELLS
ANIMALS
BODY
CARBOHYDRATES
CELL CONSTITUENTS
CHLORIDES
CHLORINE COMPOUNDS
CONNECTIVE TISSUE CELLS
DIGESTIVE SYSTEM
GLANDS
GLOBULINS
GLUCOPROTEINS
HALIDES
HALOGEN COMPOUNDS
KINETICS
MAMMALS
MEMBRANES
METALLOPROTEINS
ORGANIC COMPOUNDS
ORGANS
PHAGOCYTES
REACTION KINETICS
RODENTS
SACCHARIDES
SODIUM COMPOUNDS
SOMATIC CELLS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques