ISSN:
1573-7446
Keywords:
cattle
;
nortestosterone
;
pharmacokinetics
;
residues
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The synthetic androgen 19-nortestosterone (β-NT) has been used illegally as a growth promoter in cattle production in the European Union. Elimination of β-NT and its metabolites in plasma, urine and bile was studied in three cattle with cannulated gallbladders following intramuscular injection at a single site of 500 mg of the laurate ester (NTL) containing 300.5 mg β-NT. Using enzyme immunoassay quantification, plasma Cmax of free β-NT was 0.5±0.15 μg/L (mean±SEM). Concentrations of free β-NT in plasma were consistently greater than the assay limit of quantification (0.12 μg/L) for 32.7±13.42 days. Mean residence time for free β-NT in plasma was 68.5±20.75 days. Following sample preparation by immunoaffinity chromatography, high-resolution GC-MS was used to quantify β-NT and α-NT in urine and bile. β-NT was detected irregularly in urine from two of the three animals post injection. The principal metabolite present in the urine, α-NT, was detected for 160.3±22.67 days post injection. Cmax for α-NT in urine was 13.7±5.14 μg/L. Mean urinary AUC0–183 days for α-NT was 845.7±400.90 (μg h)/L. In bile, α-NT was the only metabolite detected for 174.3±8.67 days post treatment. Cmax for α-NT in bile was 40.8±12.70 μg/L and mean biliary AUC0–183 days for α-NT was 1982.6±373.81 (μg h)/L. Concentrations of α-NT in bile samples were greater than those in urine samples taken at the same time. The mean ratio of biliary:urinary AUC0–183 days was 3.0±0.72. It is concluded that bile is a superior fluid for detection of α-NT following injection of NTL, owing to the longer period during which residues may be detected after administration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006179116231
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