Simultaneous determination of methionine sulfoxide and methionine in blood plasma using gas chromatography-mass spectrometry.
Methionine sulfoxide is an oxidation product of methionine with reactive oxygen species via 2-electron-dependent mechanism. Such oxidants can be generated from activated neutrophils; therefore, methionine sulfoxide can be regarded as a biomarker of oxidative stress in vivo. We describe here a method for the simultaneous determination of methionine sulfoxide and methionine in blood plasma using gas chromatography-mass spectrometry with isotopically labeled compounds as internal standards. This method comprises the inclusion of [Me-13C, Me-2H(3)]methionine sulfoxide and [Me-13C, Me-2H(3)]methionine into plasma, the removal of plasma proteins using acetonitrile, the purification of amino acids with cation-exchange chromatography, and the derivatization of methionine sulfoxide and methionine to their corresponding tert-butyldimethylsilyl derivatives using N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide. Quantitation was performed by electron impact mode. The levels of methionine sulfoxide in healthy human blood plasma were 4.0 +/- 1.0 microM (means +/- SD, n = 8), indicating that approximately 10% of methionine is detected as the oxidized form in healthy human plasma. The ratio of methionine sulfoxide in total methionine increased with treatment of human blood with phorbol 12-myristate 13-acetate, while this ratio remained constant in plasma from alloxan-induced hyperglycemic rabbits. These results indicate that this method is applicable for plasma samples and methionine sulfoxide can represent oxidative stress caused by nonradical oxidation in vivo.
Mashima
Ryuichi
R
Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8904, Japan. mashima@bioreg.kyushu-u.ac.jp
Nakanishi-Ueda
Takako
T
Yamamoto
Yorihiro
Y
D000818:Animals; D002247:Carbon Isotopes; D003903:Deuterium; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008715:Methionine / Q000031:analogs & derivatives* / Q000032:analysis* / Q000097:blood
D002247:Carbon Isotopes; D008715:Methionine; D003903:Deuterium; C013111:methionine sulfoxide