Evaluation of peptide adsorption-controlled liquid chromatography-tandem mass spectrometric (PAC-LC-MS/MS) method for simple and simultaneous quantitation of amyloid β 1-38, 1-40, 1-42 and 1-43 peptides in dog cerebrospinal fluid

To evaluate the usefulness of the peptide adsorption-controlled liquid chromatography-tandem mass spectrometry (PAC-LC-MS/MS) for reproducible measurement of peptides in biological fluids, simultaneous quantitation of amyloid beta 1-38, 1-40, 1-42 and 1-43 peptides (A beta 38, A beta 40, A beta 42 and A beta 43) in dog cerebrospinal fluid (CSF) was tried. Each stable isotope labeled A beta was used as the internal standard to minimize the influence of CSF matrix on the reproducible A beta quantitation. To reduce a loss of A beta during the pretreatment procedures, the dog CSF diluted by water-acetic acid-methanol (2:6:1, v/v/v) was loaded on PAC-LC-MS/MS directly. Quantification of the A beta in the diluted dog CSF was carried out using multiple reaction monitoring (MRM) mocie. The [M+5H5(+)] and b(5+) ion fragment of each peptide were chosen as the precursor and product ions for MRM transitions of each peptide. The calibration curves were drawn from A beta standard calibration solutions using PAC-LC-MS/MS. Analysis of dog CSF samples suggests that the basal concentration of A beta 38, A beta 40, A beta 42 and A beta 43 in dog CSF is approximately 300, 900, 200 and 30 pM, respectively. This is the first time A beta concentrations in dog CSF have been reported. Additionally, the evaluation of intra- and inter-clay reproducibility of analysis of A beta standard solution, the freeze-thaw stability and the room temperature stability of A beta standard solution suggest that the PAC-LC-MS/MS method enables reproducible A beta quantitation. (C) 2012 Elsevier B.V. All rights reserved.