Development of a rapid method for the analysis of synthetic growth promoters in bovine muscle using liquid chromatography tandem mass spectrometry

[Analytical Method for Melengestrol Acetate in Livestock Products Using LC-MS/MS]

The present study verified that it is possible to analyze melengesterol acetate using the existing multi-residue method. Melengestrol acetate was extracted from livestock products using acidic acetonitrile acidified with acetic acid in the presence of n-hexane and anhydrous sodium sulfate. The crude extracts were cleaned up using an octadecylsilanized silica gel cartridge column. Separation by HPLC was performed using an octadecylsilanized silica gel column with linear gradient elution of 0.1 vol% formic acid and acetonitrile containing 0.1 vol% formic acid. For the determination of the analyte, tandem mass spectrometry with positive ion electrospray ionization was used. In recovery tests using four livestock products fortified with maximum residue limits levels of melengestrol acetate (0.001-0.02 mg/kg), the truenesses ranged from 82% to 100%, and the repeatabilities for the entire procedure ranged from 0.5 RSD% to 5.6 RSD%. In recovery tests using 11 livestock products fortified with 0.0005 mg/kg of melengestrol acetate, the truenesses ranged from 88% to 99%, and the repeatabilities ranged from 1.3 RSD% to 5.4 RSD%. The limit of quantification for melengestrol acetate in livestock products was 0.0005 mg/kg.

Oral exposure of rats to dienestrol during gestation and lactation: Effects on the reproductive system of male offspring

This study was aimed at determining whether dienestrol (DIES) affects reproduction in male offspring of rats following oral maternal exposure during gestation and lactation. Pregnant rats were treated from GD 6 to PND 21. Animals received 0 (control-vehicle), 0.75, 1.5, 3.12, 6.25, 12.5, 50, 75 μg/kg bw/d of DIES. A control group -without vehicle-was also included. High DIES concentrations caused abortions at 75 and 50 μg/kg bw/d, while at 12.5 μg/kg bw/d had still miscarriages. Ten male rats per group were kept alive until PND 90 to ensure sexual maturity. Body and organ weights, anogenital distance (AGD) at PNDs 21 and 90, biochemical and sperm parameters like motility, viability, morphology, spermatozoa and resistant spermatid counts, and histopathology for sexual organs and liver were determined. An increase in organ weight (liver and sexual organs) and a decrease in AGD due to vehicle were found. A reduction of sperm motility and viability, and an increase of abnormal sperm morphology were caused by DIES, which provoked a dose-dependent prostatitis. Maternal exposure to DIES induced toxicity on the reproductive system of the male offspring, which could affect the capacity of fertilization.

A novel megestrol acetate electrochemical sensor based on conducting functionalized acetylene black-CeO2NPs nanohybrids decorated glassy carbon microspheres

For the first time, megestrol acetate (MGA), a synthetic progestin with therapeutic use in breast cancer, is electrochemically studied to propose a new electroanalytical alternative for its detection in real samples. In the present work, a novel electrochemical sensor based on functionalized acetylene black-CeO₂NPs nanohybrids modified glassy carbon microspheres paste electrode (FAB-CeO₂NPs/GCMPE) was successfully fabricated and used for sensitive determination of MGA. The modified electrode has been characterized using scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrocatalytic reduction of MGA using FAB-CeO₂NPs/GCMPE was carried out via CV and square wave voltammetry (SWV). By employing FAB-CeO₂NPs/GCMPE, the SWV signal of MGA reduction was 8 fold higher than the bare GCMPE. A wide concentration range from 4.20 × 10^-8 to 1.13 × 10^-6 M with the low LOD of 1.30 nM for MGA was achieved. The practical analytical utilities of the prospective FAB-CeO₂NPs/GCMPE sensor were demonstrated successfully by the detection of MGA in Megace tablets, human serum and urine samples obtained from healthy and patient volunteers after oral administration of 160 mg Megace tablets. HPLC method was also developed for comparison with the electroanalytical method.

Homologous ELISA for measurement of medroxyprogesterone acetate in serum

In order to develop ELISA for medroxyprogesterone acetate, medroxyprogesterone acetate-3-carboxymethyloxime (MPA-3-CMO) was coupled to bovine serum albumin (BSA) for immunogen preparation and to horseradish peroxidase (HRP) for enzyme conjugate preparation by N-hydroxysuccinimide mediated carbodiimide reaction. The immunogen was used to raise the antiserum in New Zealand white rabbit. The immunoreactivity of MPA-3-CMO-BSA-antibody and MPA-3-CMO-HRP enzyme conjugate was checked by checkerboard assay. The MPA-3-CMO-HRP enzyme conjugate and MPA-3-CMO-BSA-antibody were used for further development, standardization and validation of the assay. Sensitivity, ED₅₀ and affinity of the assay were found to be 0.114 ng/mL, 2.75 ng/mL and 9.9 × 10⁻⁸ L/mol respectively. The % cross-reaction of analogous steroids with MPA-3-CMO-BSA-antibody was less than 0.025%. The recovery of the exogenously spiked MPA serum pools were in the range of 96.83-105.47%. The intra- and inter-assay coefficients of variation was less than 7.02%. The correlation coefficient of the serum level of MPA measured by the developed assay with the commercially available kit was found to be 0.95 (n = 37). This developed ELISA was further validated by measuring serum level of MPA in rat after administering them different doses of MPA intramuscularly.

Assessing placental corticotrophin-releasing hormone disruption by hexestrol in a cell model

Studies have shown that corticotrophin-releasing hormone (CRH) and relaxin are associated with early delivery. Our lab previously has shown the mycotoxin zeranol increases placental CRH expression. The mycotoxin is used in the farming industry to promote cattle growth, and some synthetic hormones are also used for the same purposes. In order to complete the picture of these growth promoting agents, we attempted to examine the synthetic hormones on the placental gene expression in the current study. Among the tested compounds, hexestrol induced the CRH mRNA and protein expression at 100nM in JEG-3 cells. As signal transduction pathways have been described in the transcriptional control previously, the activations of several protein kinases were determined. P38, PKCβ and JNK were activated upon hexestrol treatment. Since the P38-inhibitor SB203580 prevented hexestrol from inducing CRH in a subsequent experiment, P38 was likely involved in the transcriptional regulation. Electrophoretic mobility shift assay revealed an increase in the CRE binding activity in CRH promoter. This study showed that hexestrol exposure might be a concern for pregnant women.

Evaluation of the discriminative potential of a novel biomarker for estradiol treatments in bovine animals

The endogenous occurrence of natural hormones obstructs the application of classical targeted methods as confirmatory options. In the case of estradiol, the ultimate confirmation of its exogenous administration relies on gas chromatography coupled to combustion/isotope ratio mass spectrometry (GC-C/IRMS). A serum dipeptide composed of pyroglutamic acid and phenylalanine was identified as a potential biomarker of estradiol treatments in adult cows. To evaluate its potential to pinpoint suspicious samples, samples from prepubertal females under different estrogenic treatments have been analyzed. The results confirmed the up-regulation of the dipeptide in adult bovines. The 2-week-old females exhibited short-lasting responses only in a few animals. The 6-month-old female showed a delayed but clear increase on the biomarker level. The composition of the anabolic preparations, the dose, and/or the administration route are possible additional reasons for the reduced response in young animals. A comparison to previous results reported by various researchers is included.

Analytical investigations about the presence of prednisolone in cow urine

Since 2008, the analyses carried out in the Lombardia region as part of National Residue Control Plans have evidenced unexpected frequent detection of the corticosteroid prednisolone (PRED) in cow urine samples taken to the slaughterhouse. Considering the scarce plausibility of these high frequent findings, analytical investigations were started to ascertain the real presence of this corticosteroid. The applied confirmatory method involved liquid-chromatography low-resolution tandem mass spectrometry (triple quadrupole) as instrumental technique, and it was validated in compliance with the requirements of the Commission Decision 2002/657/EC. However, recently some criticism regarding Commission Decision 2002/657/EC identification criteria has been pointed out, experimentally demonstrating false positive results (wrong identification) although these criteria have been strictly observed. Therefore, considering the serious implications (i.e. the possibility that PRED could be considered endogenous in particular animal conditions), studies were carried out to investigate the reliability of PRED identification through the change of the chromatographic conditions (mobile phases, gradient and analytical column) of the confirmatory procedure routinely applied. Further confirmation came from the application of high-resolution mass spectrometry technique (MS(2) and MS(3) experiments) to analyze incurred cow urines samples. All the obtained results confirmed definitively the real presence of this corticosteroid excluding false-positive findings in routine analysis. In addition, other experiments demonstrated that high-resolution mass spectrometers (Time of Flight and Orbitrap technologies) could be successfully applied to routine determination of steroid residues in biological fluids at very low concentrations (< 1 µg L(-1)).

Mass spectrometric identification and characterization of new fluoxymesterone metabolites in human urine by liquid chromatography time-of-flight tandem mass spectrometry

In this study fluoxymesterone urinary profiles were investigated by liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QTOFMS) with accurate mass measurement. Twelve metabolites including the parent drug were detected in two fluoxymesterone positive control urine samples. Three parameters were employed for evaluation of the accuracy of the chemical formulae in positive full scan experiment, which contained error between actual and calculated mass weights of prontonated and isotopic molecules together with abundance match between prontonated and isotopic molecules. The 13 analytes were determined with mass accuracy less than 1.1 ppm and isotopic abundance match more than 94 marks. Based on the ionization, CID fragmentation, the accurate mass of the product ion and comparison of the accurate mass weight and retention time with reference standard, fluoxymesterone and its 12 metabolites containing three unreported ones were detected. The chemical structures of three unreported metabolites were identified as: 9-fluro-17β-ol-17-methyl-11-en-5α-androstan-3-one (F13), 9-fluro-17β-ol-17-methyl-11-en-5β-androstan-3-one (F8) and 9-fluro-17β-ol-17-methyl-5-androstan-3,6,11-trione, and meanwhile a dihydroxylated metabolite (F12), 6,16-dihydroxylated fluoxymesterone, was also detected in human urine, which was previously reported to be available only in equine urine.

Improvement of estradiol esters monitoring in bovine hair by dansylation and liquid chromatography/tandem mass spectrometry analysis in multiple reaction monitoring and precursor ion scan modes

RATIONALE

The control of forbidden anabolic practices in cattle in the European Union has become challenging since endogenous compounds such as estradiol derivatives can potentially be used as growth promoters. Due to the great difficulty in establishing a reference threshold value for endogenous steroids, the direct detection of steroid esters in hair is an efficient strategy for the detection of 'natural' steroid abuse in cattle.

METHODS

The present study aimed to develop and validate according to the current European standards a specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) analytical strategy to monitor estrogen esters in bovine hair. The analysis was performed by positive ion electrospray ionisation (ESI+) after dansylation. Two acquisition modes were then assessed: single reaction monitoring and precursor ion scanning.

RESULTS

The results showed that the introduction of a dansylation step strongly improves the sensitivity of the detection of estradiol-17-esters by LC/(ESI+)-MS/MS. The CCα values are in the range 1-10 ng g(-1) after optimisation, except for estradiol decanoate for which the derivatisation is not efficient. In addition, this LC/MS/MS approach makes it possible to carry out a precursor ion scan to screen for the presence of these estradiol 17-esters in hair samples.

CONCLUSIONS

Based on the specific product ions, i.e. m/z 255 in native conditions or m/z 171 after dansylation, this strategy has the advantage of detecting any (un)known estradiol ester and of giving access to the [M + H](+) ion of the suspected ester through only a single analysis.

Surveillance study of a number of synthetic and natural growth promoters in bovine muscle samples using liquid chromatography-tandem mass spectrometry

A simple, new method permitting the simultaneous determination and confirmation of trace residues of 24 different growth promoters and metabolites using liquid chromatography-mass spectrometry was developed and validated. The compounds were extracted from bovine tissue using acetonitrile; sodium sulphate was also added at this stage to aid with purification. The resulting mixture was then evaporated to approximately 1 ml and subsequently centrifuged at high speed and an aliquot injected onto the LC-MS/MS system. The calculated CCα values ranged between 0.11 and 0.46 µg kg(-1); calculated CCβ were in the range 0.19-0.79 µg kg(-1). Accuracy, measurement of uncertainty, repeatability and linearity were also determined for each analyte. The analytical method was applied to a number of bovine tissue samples imported into Ireland from third countries. Levels of progesterone were found in a number of samples at concentrations ranging between 0.28 and 30.30 µg kg(-1). Levels of alpha- and beta-testosterone were also found in a number of samples at concentrations ranging between 0.22 and 8.63 µg kg(-1) and between 0.16 and 2.08 µg kg(-1) respectively.

Studies on the presence of natural and synthetic corticosteroids in bovine urine

Natural and synthetic corticosteroids are widely used in veterinary medicine for their anti-inflammatory properties, but are also illegally used in animal breeding as growth-promoting agents: this latter application in livestock production has been banned within the European Union due to health concerns for the consumer. In this work urine samples collected from bovines experimentally treated with dexamethasone (0.4 mg of dexamethasone 21-disodium phosphate per capita/day for 20 consecutive days) and bovines bred under strictly controlled conditions were investigated for the presence of natural and synthetic corticosteroids, using a simple multi-residue liquid chromatography-tandem mass spectrometry method, developed and validated in accordance with the criteria of the Commission Decision 2002/657/EC. The aim of this work is to investigate the effect of a low dosage and long term dexamethasone treatment on the levels of endogenous corticosteroids in cattle and to evaluate the possible presence of prednisolone residues in bovines bred under strictly controlled conditions. Our findings confirm the high and rapid rate of dexamethasone urinary excretion. Dexamethasone treatment elicited an early reduction of hydrocortisone and cortisone, suggesting the disappearance of these two hormones as an indirect indicator of corticosteroid treatment in cattle. Prednisolone residues were found (concentration interval 0.4-1.4 ngmL(-1)) in urine samples collected from control bovines especially at the slaughterhouse, together with high levels of hydrocortisone and cortisone. Further studies are necessary to find out the reason of unexplained excretion of this hormone in urine samples of untreated bovines.

Confirmatory analysis of steroids in muscle using liquid chromatography-tandem mass spectrometry

A method is described for screening and confirmation of synthetic and endogenous steroids in muscle tissue. The method is sensitive, selective, and rapid and the consumption of organic solvents is low, compared to previously published methods. The procedure involves hydrolysis, defattening with heptane and final clean up with SPE using C(18) cartridge. After filtration, the analytes are analysed by LC/MS/MS and quantification is performed using deuterated internal standards. Decision limits (CCα) varied from 0.02 to 0.33 µg kg(-1) and the detection capabilities (CCβ) were <0.50 µg kg(-1). The mean within-laboratory reproducibility ranged 5-22% (%RSD(IR)). Endogenous steroids (e.g. testosterone, epitestosterone and androstenedione) have been included in the method, to provide an insight into their levels, as the presence of these steroids was detected several times during analysis of imported meat.