TRANSFERRIN RECEPTORS OF RAT AND HUMAN BRAIN AND CEREBRAL MICROVESSELS AND THEIR STATUS IN ALZHEIMERS-DISEASE

We studied the regional distribution of specific [I-125]transferrin binding to transferrin receptors in the brains and cerebral microvessels of humans and rats. We also assessed transferrin receptors in subjects with Alzheimer's disease. Human diferric [I-125]transferrin bound to regional brain and cerebral microvessels with high affinity (dissociation constants of 1-10 nM), and the maximal binding densities ranged from 30 to 90 pmol/mg protein in the brain and were several-fold higher in cerebral microvessels. In Alzheimer's disease, transferrin receptor densities were significantly reduced in the hippocampus and the temporal and occipital cortex but were unchanged in the frontal and parietal cortex and the cerebellum. Although [I-125]transferrin binding was higher in cerebral microvessels from subjects with Alzheimer's disease than in those of age-matched controls, this difference did not attain statistical significance. These results suggest that transferrin receptor density was decreased in some cortical areas including the hippocampus in Alzheimer's disease but relatively unchanged in cerebral microvessels.