Secretory form of beta-amyloid precursor protein is much abundantly contained in the cerebral white matter in human brain.

To elucidate the metabolic process of beta-amyloid precursor proteins (APP) in cerebral gray and white matter of the human brain, we compared the content and characteristics of secretory APP between these two parts. The white matter contained much more secretory APP than the gray matter in both a control and a Down's syndrome brain, but no difference in the characteristics of the APP isoforms was detected. Our results suggest that, in the human brain, a considerable amount of APP is carried by axonal transport, during which some of the APP isoforms are processed to their secretory forms.