Mass spectrometric characterization of tamoxifene metabolites in human urine utilizing different scan parameters on liquid chromatography/tandem mass spectrometry.
ABSTRACT Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were considered for the characterization of tamoxifene metabolites in human urine for anti-doping purpose. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 166, 152 and 129) and neutral loss scan (neutral loss of 72 Da and 58 Da) in positive ion mode were assessed to recognize common ions or common losses of tamoxifene metabolites. The applicability of these methods was checked first by infusion and then by the injection of solution of a mixture of reference standards of four tamoxifene metabolites available in our laboratory. The data obtained by the analyses of the mixture of the reference standards showed that the five methods used exhibited satisfactory results for all tamoxifene metabolites considered at a concentration level of 100 ng/mL, whereas the analysis of blank urine samples spiked with the same tamoxifene metabolites at the same concentration showed that the neutral loss scan of 58 Da lacked sufficient specificity and sensitivity. The limit of detection in urine of the compounds studied was in the concentration range 10-100 ng/mL, depending on the compound structure and on the selected product ion. The suitability of these approaches was checked by the analysis of urine samples collected after the administration of a single dose of 20 mg of tamoxifene. Six metabolites were detected: 4-hydroxytamoxifene, 3,4-dihydroxytamoxifene, 3-hydroxy-4-methoxytamoxifene, N-demethyl-4-hydroxytamoxifene, tamoxifene-N-oxide and N-demethyl-3-hydroxy-4-methoxytamoxifene, which is in conformity to our previous work using a time-of-flight (TOF) mass spectrometer in full scan acquisition mode.
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ABSTRACT: Androgens can increase muscular mass and strength and remain the most frequently abused and widely available drugs used in sports doping. Banning the administration of natural or synthetic androgens has led to a variety of strategies to circumvent the ban of the most effective ergogenic agents for power sports. Among these, a variety of indirect androgen doping strategies aiming to produce a sustained rise in endogenous testosterone have been utilized. These include oestrogen blockade by drugs that act as oestrogen receptor antagonists (antioestrogen) or aromatase inhibitors. The physiological and pharmacological basis for the effects of oestrogen blockade in men, but not women, are reviewed.British Journal of Pharmacology 07/2008; 154(3):598-605. · 5.07 Impact Factor
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ABSTRACT: A molecular modelling study on the human cytochrome P450-mediated metabolism of tamoxifen is reported. Using three-dimensional models of human P450s constructed from the bacterial crystal structure template, P450bm3 (CYP102), the likely mode of substrate binding is demonstrated, which is consistent with the known positions of metabolism in tamoxifen. In particular, the CYP102-derived structures of CYP3A4, CYP2D6 and CYP2C9 are able to rationalize the routes of tamoxifen metabolism reported in human subjects. The implications for potential toxicity of tamoxifen in man is discussed in the light of these findings.Carcinogenesis 07/1996; 17(6):1357-60. · 5.64 Impact Factor
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ABSTRACT: This paper describes a liquid chromatographic/tandem mass spectrometric (LC/MS-MS) method specifically designed for the screening of synthetic glucocorticosteroids in human urine. The method is designed to recognize a common mass spectral fragment formed from the particular portion of the molecular structure that is common to all synthetic glucocorticosteroids and that is fundamental to their pharmacological activity. As such, the method is also suitable for detecting unknown substances, provided they contain the portion of the molecular structure selected as the analytical target. The effectiveness of this approach was evaluated on seventeen synthetic glucocorticosteroids. Urine samples, including blank urines spiked with one or more synthetic glucocorticosteroids, were treated according to a standard procedure (enzymatic hydrolysis, liquid/liquid extraction and evaporation to dryness) and analyzed using LC/MS-MS with electrospray ionization (ESI). MS-MS acquisition was carried out in a precursor ion scan, and the results were compared with those obtained by a previously developed reference technique based on acquisition in the multiple reaction monitoring (MRM) mode. All of the glucocorticosteroids considered in this study are clearly detectable in urine, with a limit of detection in the concentration range 5-20 ng/mL, depending on the glucocorticosteroid structure. The proposed method is therefore suitable for the detection of glucocorticosteroids in urine samples taken for "in competition" sport anti-doping control tests, matching the requirements of the World Anti-Doping Agency (WADA) for accredited anti-doping laboratories.Analytical and Bioanalytical Chemistry 04/2008; 390(5):1389-402. · 3.66 Impact Factor