Serum amyloid P is not present in amyloid beta 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 AD 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 (betaPP). 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.