MASS-SPECTROMETRIC QUANTIFICATION OF 3-CHLOROTYROSINE IN HUMAN TISSUES WITH ATTOMOLE SENSITIVITY - A SENSITIVE AND SPECIFIC MARKER FOR MYELOPEROXIDASE-CATALYZED CHLORINATION AT SITES OF INFLAMMATION

Oxidative modification of proteins has been implicated in a variety of processes ranging from atherosclerosis to aging. Identifying the unde rlying oxidation pathways has proven difficult, however, due to the la ck of specific markers for distinct oxidation pathways. Previous in vi tro studies demonstrated that 3-chlorotyrosine is a specific product o f myeloperoxidase-catalyzed oxidative damage and that the chlorinated amino acid may thus serve as an index of phagocyte-mediated tissue inj ury in vivo. Here we describe a highly sensitive and specific analytic al method for the quantification of 3-chlorotyrosine content of tissue s. The assay combines gas chromatography with stable isotope dilution mass spectrometry, and it detects attomole levels of 3-chlorotyrosine in a single determination. Furthermore, the method is highly reproduci ble, with inter-and intra-sample coefficients of variance of < 3%. The specificity, sensitivity, and reproducibility of 3-chlorotyrosine det ermination should make this method useful for exploring the role of my eloperoxidase in catalyzing oxidative reactions in vivo. (C) 1997 Else vier Science Inc.