Serum amyloid A is present in the capillaries and microinfarcts of hypertensive monkey brain: an immunohistochemical study

Serum amyloid A (SAA) is a major inducible acute phase protein characterize d as a transient injury specific constituent of high density lipoprotein. W e investigated whether the acute phase SAA (A-apoSAA), as a marker of infla mmation, is present in the brain of monkeys with surgically induced hyperte nsion of 39 months duration. Sections from brains of normotensive monkeys ( systolic blood pressure<124 mmHg) and hypertensive monkeys (systolic blood pressure>185 mmHg) were processed for immunohistochemistry with a rabbit po lyclonal antiserum to human A-apoSAA. We found that A-apoSAA was present in hypertensive but not in normotensive brain sections. Staining was localize d to capillary endothelial cells and occasionally to the entire vessel wall of the prefrontal cortex. Staining was also observed in the capillaries an d in medium size vessels of the corona radiata, the head of the caudate and , to a smaller extent, in the putamen. Additionally, the A-apoSAA was prese nt in cells forming a circular configuration within microinfarcts. These fi ndings suggest that high blood pressure in the brain can result in either l ocal production of A-apoSAA in the capillaries and within microinfarcts or uptake of A-apoSAA from the blood.