Quantification of endogenous α- and γ-endorphins in rat brain by liquid chromatography-tandem mass spectrometry

Quantification of alpha- and gamma-endorphins in Fat brain using liquid chromatography-electrospray ionization-tandem mass spectrometry is described. [D-Ala(2)]-gamma-endorphin is used as an internal standard. The precursor-to-product ion MRM transitions for alpha-endorphin, gamma-endorphin, and [D-Ala(2)]-gamma-endorphin were m/z 873.6 -> 429.6; 929.6 -> 542.3; 936.6 -> 542.3, respectively. The method was validated in terms of linearity, Specificity, sensitivity, recovery, precision, and accuracy, The assay was linear over a concentration range of 0.1-200 ng/mL with the limit-of-detection of 0.03 ng/mL and limit-of-quantification of 0.1 ng/mL. The endogenous concentrations of alpha- and gamma-endorphins in rat brains were 13.8 +/- 0.57 (mean +/- SD; n = 5) and 2.5 +/- 0.43 ng/g of wet tissue Weight, respectively. (c) 2009 Elsevier Inc. All rights reserved.