Tissue Residues and Urinary Excretion of Zilpaterol in Sheep Treated for 10 Days with Dietary Zilpaterol

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• 作者：Weilin L. Shelver and David J. Smith
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2006
• 出版时间：June 14, 2006
• 年：2006
• 卷：54
• 期：12
• 页码：4155 - 4161
• 全文大小：95K
• 年卷期：v.54,no.12(June 14, 2006)
• ISSN：1520-5118

文摘

Zilpaterol is a mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">-adrenergic growth promoter approved in Mexico and South Africa for use in cattle.Understanding the rates of zilpaterol depletion from tissues and urine is of interest for the developmentof strategies to detect the off-label use of zilpaterol. Eight sheep were fed 0.15 mg/kg/day dietaryzilpaterol hydrochloride (Zilmax) for 10 consecutive days; two sheep each were slaughtered 0, 2, 5,and 9 days after discontinuation of exposure to the zilpaterol-containing diet. Tissue zilpaterol levelsrapidly decreased during the withdrawal period. On the basis of LC-MS/MS-ES (external standard)measurements, liver zilpaterol residues in sheep were 29.3, 1.5, 0.13, and 0.10 ng/g after 0, 2, 5,and 9 day withdrawal periods, respectively; kidney residues were 29.6, 1.10, and 0.09 ng/g and belowthe detection limit; and muscle residues were 13.3, 0.86, 0.12, and 0.08 ng/g at the same respectivewithdrawal periods. Between-animal variation in urinary zilpaterol concentrations during the feedingperiod was considerable, although zilpaterol concentrations converged somewhat as steady statewas reached. During the first 3 days of the withdrawal period, zilpaterol elimination followed a first-order excretion pattern, having an average elimination half-life of 15.3 ± 1.8 h. Urinary zilpaterolconcentrations during the withdrawal period were determined using ELISA, HPLC-fluorescence, LC-MS/MS-ES (external standard), and LC-MS/MS-IS (internal standard). Comparison of these methodsshowed a high correlation with each other. With the exception of LC-MS/MS-IS, the regressioncoefficients of the linear equations with a zero intercept were between 0.90 and 1.25, indicating thenear equivalence of the methods. Because of its simplicity, ELISA is a convenient assay for determiningzilpaterol levels in urine giving similar results to HPLC-fluorescence and LC-MS/MS-ES withoutrequiring the extensive cleanup of the latter methods.Keywords: Analysis; ELISA; HPLC; LC-MS/MS; zilpaterol; residue