Jdg. Mcevoy et al., Plasma, urinary and biliary residues in cattle following intramuscular injection of nortestosterone laurate, VET RES COM, 22(7), 1998, pp. 479-491
The synthetic androgen 19-nortestosterone (beta-NT) has been used illegally
as a growth promoter in cattle production in the European Union. Eliminati
on of beta-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
beta-NT. Using enzyme immunoassay quantification, plasma C-max of free beta
-NT was 0.5 +/- 0.15 mu g/L (mean +/- SEM). Concentrations of Free beta-NT
in plasma were consistently greater than the assay limit of quantification
(0.12 mu g/L) for 32.7 +/- 13.42 days. Mean residence time for free beta-NT
in plasma was 68.5 +/- 20.75 days. Following sample preparation by immunoa
ffinity chromatography, high-resolution CC-MS was used to quantify beta-NT
and alpha-NT in urine and bile. beta-NT was detected irregularly in urine f
rom two of the three animals post injection. The principal metabolite prese
nt in the urine, alpha-NT, was detected for 160.3 +/- 22.67 days post injec
tion. C-max for alpha-NT in urine was 13.7 +/- 5.14 mu g/L. Mean urinary AU
C(0-183 days) for alpha-NT was 845.7 +/- 400.90 (mu g h)/L.
In bile, alpha-NT was the only metabolite detected for 174.3 +/- 8.67 days
post treatment. C-max for alpha-NT in bile was 40.8 +/- 12.70 mu g/L and me
an biliary AUC(0-183 days) for alpha-NT was 1982.6 +/- 373.81 (mu g h)/L. C
oncentrations of alpha-NT in bile samples were greater than those in urine
samples taken at the same time. The mean ratio of biliary:urinary AUC(0-183
days) was 3.0 +/- 0.72. It is concluded that bile is a superior fluid for
detection of alpha-NT following injection of NTL, owing to the longer perio
d during which residues may be detected after administration.