A New Methodology For Simultaneous Quantification Of Total-A Beta, A Beta X-38, A Beta X-40, And A Beta X-42 By Column-Switching Lc/Ms/Ms

This article details the development of a novel method that overcomes the drawbacks of sandwich ELISA (sELISA) and allows reliable evaluation of simultaneous quantification of the amyloid (A beta)-peptides, total-A beta, A beta x-38, A beta x-40, and A beta x-42, in rat brain by optimized sample purification and column-switching liquid chromatographic-tandem mass spectrometry (LC/MS/MS). This method provides accurate analyses of total-A beta, A beta x-38, A beta x-40, and A beta x-42 with a linear calibration range between 0.05 and 45 ng/mL. Verification for accuracy and precision of biological samples were determined by a standard addition and recovery test, spiked with synthetic A beta 1-38, A beta 1-40, and A beta 1-42 into the rat brain homogenate. This method showed < 20% relative error and relative standard deviation, indicating high reproducibility and reliability. The brain concentrations of total-A beta, A beta x-38, A beta x-40, and A beta x-42 after oral administration of flurbiprofen in rats were measured by this method. A beta x-42 concentrations (4.57 +/- 0.69 ng/g) in rats administered flurbiprofen were lower than those in untreated rats (6.48 +/- 0.93 ng/g). This was consistent with several reports demonstrating that NSAIDs reduced the generation of A beta. We report here a method that allows not only the quantification of specific molecular species of A beta but also simultaneous quantification of total-A beta, A beta x-38, A beta x-40, and A beta x-42, thus overcoming the drawbacks of sELISA.