Accumulation of apolipoprotein E and beta-amyloid-like protein in a trace of the hippocampal CA1 pyramidal cell layer after ischaemic delayed neuronal death

We found that apolipoprotein E (apo E) accumulates in a trace of the hippocampal CA1 pyramidal cell layer within 6 months after 5 min ischaemia. Intense methenamine-silver (M-S) stainings were seen in the entire CA1 subfield 3 months after ischaemia. The M-S staining pattern may imply the appearance of soluble A beta-like proteins. The apo E-positive trace was also positively stained with anti-beta-amyloid (A beta) protein antibodies, but not with anti-beta-amyloid protein precursor (APP) antibodies. These results suggest that A beta-like protein accumulates in ischaemic brain after neuronal cell death. Adjacent reactive astrocytes showed both apo E- and A beta-immunoreactivities. These astrocytes may be involved in the clearance of apo E- and A beta-positive material. We presume that the coincident distribution pattern for apo E- and A beta-immunoreactivity implies formation of the insoluble and stable A beta-apo E complex which is known to exist in the brain of individuals with Alzheimer's disease. The ischaemic model may he useful in studying apo E and A beta deposition in the brain.