Quantifying Murine Aβ Levels by ELISA

Murine Aβ levels were determined by sandwich ELISA using aliquots of the 10% sucrose homogenate. Soluble Aβ from an aliquot of the sucrose homogenates of wild-type and Tg2576 mice was extracted by diethylamine (DEA) [48] (link); separately, formic-acid extraction of another aliquot of the sucrose homogenate was used to detect β-amyloid plaque-associated Aβ in the Tg2576 mice. In combination with Aβ40 and Aβ42 C-terminal specific monoclonal antibodies (capture antibodies JRF/cAβ40/10 and JRF/cAβ42/26) [49] (link), horseradish peroxidase-conjugated m3.2 was used to detect endogenous murine Aβ in Aβ40- and Aβ42-specific sandwich ELISAs [50] (link). Similar ELISAs using JRF/AβN25 [51] (link) were used to detect human Aβ in the Tg2576 mouse brains. ELISA results are reported as the mean ± SEM in fmol Aβ per g wet brain, based on standard curves using synthetic murine and human Aβ1−40 and Aβ1−42 peptide standards (American Peptide).