An intracarotid brain infusion/capillary depletion technique was used in guinea pigs to examine cerebral capillary sequestration and transport into brain parenchyma of sAβ1–40 and sAβ1–42, synthetic peptides identical to two forms of the amyloid β peptide found in Alzheimer's disease lesions: the 40 residue form, found primarily in vascular deposits, and the 42 residue form, found primarily in senile plaques. The peptides crossed well into the brain parenchyma via a specific transport mechanism for which sAβ1–40 had an approximately two-fold greater affinity than sAβl–42. There was significant capillary sequestration of sAβ1–40, but retention by the microvasculature of sAβ1–42 was negligible. These data suggest that the level of the 40 residue peptide in cerebral vasculature and of the 42 residue peptide in parenchyma could be regulated by blood-brain barrier sequestration and transport of their respective circulating precursors.
This work was supported by the National Institutes of Health Grants NS34467 and AG10953. We wish to thank Dr. Blas Frangione for his valuable insight and suggestions.