Measurement of acute phase proteins in the rat brain: contribution of vascular contents.

A localized acute phase response occurs in the brain in Alzheimer's disease. Acute phase proteins have previously been measured in brain homogenates to quantify this response. The extent to which measurements of these proteins reflect brain parenchymal contents, as opposed to vascular contents, is unknown. In this study, the acute phase proteins ceruloplasmin (CP), complement factor 3 (C3), haptoglobin (HP), and albumin were measured in regional brain homogenates from phosphate buffered saline-perfused and sham-perfused rats (n = 7-9/group). Interleukin 1-beta (IL1-beta) and copper were also measured. Mean CP, C3, HP, and albumin concentrations in perfused specimens decreased by 94%, 88%, 90%, and 81% vs. sham-perfused specimens (all p < 0.001), while IL1-beta and copper were unchanged. These results suggest that acute phase protein measurements in brain homogenates reflect primarily vascular contents. However, IL1-beta and copper concentrations in brain homogenates are minimally influenced by vascular contents.