A specific radioimmunoassay for the detection of 19-nortestosterone residues in urine and plasma of cattle

Development of a multianalyte method for the determination of anabolic hormones in bovine urine by isotope-dilution GC–MS/MS

A sensitive, specific and selective multianalyte GC-MS/MS method has been developed for the determination of 11 anabolic hormones in bovine urine. After adjusting the urine pH to 4.8, the samples were spiked with deuterated internal standards and submitted to enzymatic hydrolysis with beta-glucuronidase/arylsulfatase. Hormones were eluted with methanol through a C18 solid phase cartridge and submitted to a liquid-liquid extraction. Analytes were derivatized by adding N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane and GC-MS data were obtained in the positive electron impact tandem mass mode. Under these conditions, no matrix effects were observed and limit of detection values were in the range of 0.005 ng/mL (diethylstilbestrol) to 0.38 ng/mL (17alpha-methyltestosterone and 17alpha-ethynylestradiol). Recoveries from 81% (alpha-zeranol) to 149% (17alpha-methyltestosterone) were found under the selected conditions. These results were better than those found using heptafluorobutyric anhydride (HFBA) as derivative reagent and those measured in full scan and selective ion monitoring modes.

A rapid and sensitive 384-well microtitre format chemiluminescent enzyme immunoassay for 19-nortestosterone

We developed a competitive chemiluminescent (CL) enzyme immunoassay for rapid, sensitive analysis of 19-nortestosterone (19-NT) in bovine urine. Anti-19-NT polyclonal antibodies were raised in rabbits using a 19-NT-hemisuccinate derivative conjugated with ovalbumin; the derivative was also conjugated with horseradish peroxidase (HRP) as a label. Antibodies were immobilized on 384-well black polystyrene microtitre plates and HRP-labelled 19-NT activity was measured using an efficient chemiluminescent substrate (SuperSignal ELISA Femto) after 3 min incubation. Emitted light was recorded using a conventional, photomultiplier-tube-based microtitre plate reader or a sensitive back-illuminated, cooled CCD camera. The developed method fulfils all the requirements of precision (intra- and inter-assay CV < 10%) and accuracy (mean recovery 94-112%), with a detection limit of 0.03 ppb (1.1 x 10(-9) mol/L) in a urine matrix. Chemiluminescence enhances detectability of the HRP-labelled tracer (thus lowering the limit of detection with respect to colorimetry) and reduces analysis time. The 384-well microtitre plate cuts the sample/reagent volume (20 microL), a five-fold reduction with respect to the conventional 96-well microtitre plate. The developed method is suitable for high-throughput screening of 19-NT in urine samples, with reduced costs as compared with conventional colorimetric enzyme immunoassays.

Quantitation of anabolic hormones and their metabolites in bovine serum and urine by liquid chromatography-tandem mass spectrometry

A specific and sensitive method based on tandem mass spectrometry with on-line high-performance liquid chromatography using atmospheric pressure chemical ionisation (LC-APCI-MS-MS) for the quantitation of anabolic hormone residues (17beta-19-nortestosterone, 17beta-testosterone and progesterone) and their major metabolites (17alpha-19-nortestosterone and 17alpha-testosterone) in bovine serum and urine is reported. [2H2]17Beta-testosterone was used as internal standard. The analytes were extracted from urine (following enzymatic hydrolysis) and serum samples by liquid-liquid extraction and purified by C18 solid-phase extraction. Ionisation was performed in a heated nebulizer interface operating in the positive ion mode, where only the protonated molecule, [M+H]+, was generated for each analyte. This served as precursor ion for collision-induced dissociation and two diagnostic product ions for each analyte were identified for the unambiguous hormone confirmation by selected reaction monitoring LC-MS-MS. The overall inter-day precision (relative standard deviation) ranged from 6.37 to 2.10% and from 6.25 to 2.01%, for the bovine serum and urine samples, respectively, while the inter-day accuracy (relative error) ranged from -5.90 to -3.18% and from -6.40 to -2.97%, for the bovine serum and urine samples, respectively. The limit of quantitation of the method was 0.1 ng/ml for all the hormones in bovine serum and urine. On account of its high sensitivity and specificity the method has been successfully used to confirm illegal hormone administration for regulatory purposes.

Natural sex steroids and their xenobiotic analogs in animal production: growth, carcass quality, pharmacokinetics, metabolism, mode of action, residues, methods, and epidemiology

Natural and xenobiotic compounds having sex-related actions have long been used for growth promotion and various changes in carcass quality in meat animals. The first compounds used were synthetic estrogens; however, later on a whole battery of compounds having androgenic, and progestogenic actions have also been involved. In surveying the effects of these compounds in meat-producing animals, it became clear that these drugs increase the growth rate of the treated animals and bring about changes in the carcass that are generally characterized by lower fat content and more lean mass. Extensive studies undertaken in various countries, including the European Economic Community (EEC), have shown that if used according to good husbandry practices, the meat from treated animals does not have excessive amounts of residues compared with the endogenous amount of steroid production in the animals in question and also in human beings. The banning of these compounds in the European community brought a new phenomenon of illegal or black market cocktails. These mixtures of anabolic steroids are injected into the body of the animals rather than implanted in the ears, which is the normal practice in countries where they have not yet been banned. Several screening and confirmatory methods are now available for monitoring programs. However, these programs need excessive resources in terms of manpower, funds, and proper legislation, which in underdeveloped countries is questionable, particularly in the absence of strong scientific evidence for the exercise.

Combined high-performance liquid chromatography and radioimmunoassay for the screening of 19-nortestosterone and methyltestosterone residues in meat samples

A procedure is described for the detection of 17 beta-19-nortestosterone (17 beta-19-NT) and 17 alpha-methyltestosterone (17 alpha-MT) in muscle tissue by a combination of high-performance liquid chromatography and radioimmunoassay. The steroids were released from the muscle tissue by enzyme digestion, and the extracts were purified by solid-phase extraction. A meat sample from the retail trade, which was proved to contain 17 beta-19-NT and 17 alpha-MT residues by gas chromatography-mass spectrometry, and blank meat samples obtained from non-treated experimental animals were purified and the extracts injected into the liquid chromatograph. With an automatic fraction collector, fifteen fractions of 1 ml each were obtained, which after evaporation were subjected to a radioimmunoassay for the steroid concerned. It was demonstrated that none of the fractions from the blank meat samples contains any substance that interfered with the immunochemical detection system. In addition, a good qualitative agreement between the two sets of results was obtained. Although the sample preparation step is rather labour-intensive, the method can be successfully applied as a reliable confirmation method for positive radioimmunoassay screening results in circumstances where no gas chromatography-mass spectrometry facilities are available.

Identification and characterization of 19-nortestosterone in urine of meat-producing animals

To monitor the illegal use of 19-nortestosterone as an anabolizing agent in meat-production, the Belgian Institute of Veterinary Expertise applies a strategy of urine control by radioimmunoassay, positive samples being confirmed by thin-layer chromatography. We have evaluated this control strategy, using gas chromatography-mass spectrometry to confirm the presence of 19-nortestosterone, or its metabolite oestrane-diol, in positive samples from radioimmunoassay. Our results show that the effective way of proceeding remains reliable in cattle, for mature and immature males as well as non-pregnant females, and in pigs, for pregnant and non-pregnant sows. The possible presence of endogenous 19-nortestosterone in cattle, in pregnant cows urine, and in pigs, in boars and in cryptorchid pigs, impedes the control of the use of 19-nortestosterone on these samples. False-positive (not confirmed by gas chromatography-mass spectrometry) results were produced by radioimmunoassay in the urine of castrated pigs and sheep.

Development of a competitive enzyme immunoassay for 17 alpha-19-nortestosterone

Because 17 beta-19-nortestosterone and its esters are frequently used anabolic steroids in cattle in Europe, there is a need for an assay that can also detect certain metabolites. The enzyme immunoassay described here involves the detection and quantitation of the major metabolite 17 alpha-19-nortestosterone in urine. The assay is based on the coating of an antibody raised in a rabbit against 17 alpha-19-nortestosterone-3-carboxy-methyloxime-bovine serum albumin (17 alpha-19-NT-3-CMO-BSA), the competitive incubation of 17 alpha-19-NT and the 17 alpha-19-nortestosterone-3-CMO-horseradish peroxidase label, followed by the detection of the blue colour developed by the action of the enzyme on tetramethylbenzidine. The 3-CMO conjugate of 17 alpha-19-nortestosterone was used to produce an antibody with selective affinity for the 17 alpha-epimer. For the optimization of the assay, different coatings and incubation conditions were tested. The standard curve ranged between 0.98 and 4000 pg per well, with a B/B0 50% of +/- 65 pg per well. Colour was measured with a microtitre plate reader. The method was validated by means of certified blank and spiked cattle urine samples.

Gas chromatographic-mass spectrometric confirmation of 19-nortestosterone in the urine of untreated boars--effect of the administration of Laurabolin

The presence of 17 beta-19-nortestosterone (nandrolone, NT, 17 beta-19-NT) and its epimer 17 alpha-19-nortestosterone (epiNT, 17 alpha-19-NT) was investigated in the urine of six untreated boars, obtained from experimental farms. The presence of 17 beta-19-nortestosterone was screened by RIA and HPTLC and confirmed by GC-MS analysis. Additionally, the two epimers (NT and epiNT) were investigated in the urine of a boar (two-year-old miniature male pig weighing 50 kg) before and after injection of 100 mg Laurabolin (nortestosterone laurate, Intervet N.V., Belgium). The isolation of the steroids was based on sample clean-up with solid phase extraction and subsequent high-performance liquid chromatography. Both gas chromatographic retention data and mass spectrometric data (selected ion monitoring and full spectrum) were used for detection and identification. The presence of 17 beta-19-nortestosterone in the urine of the boars that were not injected proves the endogenous production of the steroid. The absence of the 17 alpha-epimer in the urine of the injected boar suggests that 17 alpha-19-nortestosterone is not a major metabolite of 17 beta-19-nortestosterone.

Enzyme immunoassay screening procedure for the synthetic anabolic estrogens and androgens diethylstilbestrol, nortestosterone, methyltestosterone and trenbolone in bovine urine

Immunoassays are often used for the screening of anabolic residues in edible tissues and excreta (urine, faeces) from inspected animals. Radioimmunoassays have been used for ten years for the determination in biological samples of the main natural and synthetic anabolic estrogens and androgens. In order to simplify the sample preparation and analysis and to reduce the cost, competitive enzyme immunoassays (EIA) were developed for the main synthetic anabolics used illegally in livestock fattening. EIA are based on a competition between the analyte (hormone or metabolite) and the enzyme-labelled hormone for binding to specific antibodies immobilized in wells of a microtitration plate. Two enzymes were evaluated: horseradish peroxidase (HRP) and Bacillus licheniformis beta-lactamase (BLL) using hydrogen peroxide-o-phenylenediamine or benzylpenicillin-starch-iodine as substrates, respectively. The same derivative was used for chemical coupling of the hormone to enzyme (tracer preparation) and to bovine serum albumin to produce specific antibodies in rabbits. Hormone doses that inhibited 50% of the tracer (HRP-hormone) binding to antibody (ID50) were 18, 8, 6 and 11 pg per well for diethylstilbestrol, nortestosterone, methyltestosterone and trenbolone, respectively. These values were lower than those observed in RIA. The reproducibility and accuracy of EIA in urine analysis were similar to those of RIA. Very small amounts of urine were needed (2.5 microliters). This simple method may require less than 2 h. With the BLL-hormone tracer, the enzymatic activity remaining in the wells and hence the hormone content of the sample could be estimated with the naked eye using benzylpenicillin-starch-iodine as substrate.