Serum amyloid P is not present in amyloid β deposits of a transgenic animal model

SERUM amyloid P component (SAP) is associated with amyloid beta (A beta) deposition in Alzheimer disease (AD). Since SAP is exclusively synthesized by peripheral organs, its presence in the brain of A beta suggests impairment of the blood-brain barrier (BBB). We studied the association of SAP with A beta deposits in a transgenic mouse model overexpressing beta-protein precursor (X PP). Both SAP and another extracellular matrix binding protein, basic fibroblastic growth factor bind to the heparinase sensitive sites of A beta deposits in this model. However, no endogenous SAP immunoreactivity was found in the transgenic mouse brain. These results suggest that SAP is not required for A beta deposition, and that this mouse model does not develop the same BBB abnormalities as those seen in AD. (C) 1999 Lippincott Williams & Wilkins.