Shelver Weilin L, Smith David J
Biosciences Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, 1605 Albrecht Boulevard, Fargo, North Dakota 58105, USA.
J Agric Food Chem. 2006 Jun 14;54(12):4155-61. doi: 10.1021/jf060552m.
Zilpaterol is a beta-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 development of strategies to detect the off-label use of zilpaterol. Eight sheep were fed 0.15 mg/kg/day dietary zilpaterol 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 levels rapidly 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 below the detection limit; and muscle residues were 13.3, 0.86, 0.12, and 0.08 ng/g at the same respective withdrawal periods. Between-animal variation in urinary zilpaterol concentrations during the feeding period was considerable, although zilpaterol concentrations converged somewhat as steady state was 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 zilpaterol concentrations 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 methods showed a high correlation with each other. With the exception of LC-MS/MS-IS, the regression coefficients of the linear equations with a zero intercept were between 0.90 and 1.25, indicating the near equivalence of the methods. Because of its simplicity, ELISA is a convenient assay for determining zilpaterol levels in urine giving similar results to HPLC-fluorescence and LC-MS/MS-ES without requiring the extensive cleanup of the latter methods.
齐帕特罗是一种β-肾上腺素能生长促进剂，在墨西哥和南非被批准用于牛。了解齐帕特罗从组织和尿液中的消耗速率对于制定检测齐帕特罗标签外使用的策略很有意义。八只绵羊连续10天每天饲喂0.15毫克/千克的盐酸齐帕特罗（Zilmax）；在停止接触含齐帕特罗的饲料后，分别在0、2、5和9天宰杀两只绵羊。在停药期间，组织中的齐帕特罗水平迅速下降。根据液相色谱-质谱/质谱-电喷雾（外标法）测量，停药0、2、5和9天后，绵羊肝脏中的齐帕特罗残留量分别为29.3、1.5、0.13和0.10纳克/克；肾脏残留量为29.6、1.10和0.09纳克/克，低于检测限；在相同的停药期间，肌肉残留量分别为13.3、0.86、0.12和0.08纳克/克。在饲喂期间，动物间尿液中齐帕特罗浓度的差异相当大，尽管随着达到稳态，齐帕特罗浓度有所趋同。在停药期的前3天，齐帕特罗的消除遵循一级排泄模式，平均消除半衰期为15.3±1.8小时。停药期间尿液中的齐帕特罗浓度通过酶联免疫吸附测定法（ELISA）、高效液相色谱-荧光法（HPLC-fluorescence）、液相色谱-质谱/质谱-电喷雾（外标法）和液相色谱-质谱/质谱-同位素内标法（LC-MS/MS-IS）进行测定。这些方法的比较显示它们之间具有高度相关性。除了液相色谱-质谱/质谱-同位素内标法外，截距为零的线性方程的回归系数在0.90至1.25之间，表明这些方法几乎等效。由于其简便性，ELISA是一种方便的测定尿液中齐帕特罗水平的方法，其结果与HPLC-荧光法和液相色谱-质谱/质谱-电喷雾法相似，且无需后两种方法那样进行大量的净化处理。
