W. Vangelder et al., QUANTIFICATION OF DIFFERENT TRANSFERRIN RECEPTOR POOLS IN PRIMARY CULTURES OF PORCINE BLOOD-BRAIN-BARRIER ENDOTHELIAL-CELLS, Journal of neurochemistry, 64(6), 1995, pp. 2708-2715
Distribution of iron in the brain varies with region, cell type, and a
ge. Furthermore, some neurological diseases are accompanied by an abno
rmal accumulation of iron in specific areas of the CNS. These findings
implicate a mobile intracerebral iron pool; however, transport of iro
n across the blood-brain barrier and its regulation are largely unknow
n. In an extensive series of experiments in primary cultures of porcin
e blood-brain barrier endothelial cells, we separately quantified surf
ace-bound and total cellular transferrin receptor pools. Although 90%
of all transferrin receptors were located inside the cell, only 10% of
these intracellular receptors actively took part in the endocytic cyc
le. This large ''inactive'' intracellular transferrin receptor pool co
uld either function as a storage site for spare receptors or be activa
ted by the cell to increase its capacity for iron transport. Data were
corrected for nonspecific binding by a separate biochemical assessmen
t using a 100-fold excess of unlabeled ligand. Data were also analyzed
in a nonlinear curve-fit program. This resulted in a less elaborate a
nd less biased estimate of nonspecific binding.