Residues and metabolism of 19-nortestosterone laurate in steers†

Abstract

The illegal use of nandrolone) and its esters in livestock, for growth promotion purposes, has been widely reported in the European Union. The target residues for surveillance of abuse in bovine urine and bile samples are 17a-and 17b-19NT, although this choice of target residues is not based on in vivo radiotracer biotransformation data. In this study, four steers were administered [ 3 H 2 ]-and [ 2 H 3 ] 17b-19NT laurate (2 mg kg 21 body mass) by intramuscular injection and blood, urine, faeces and bile samples were taken for 30 d until slaughter, after which tissues were sampled for total residue analysis. Total plasma radiolabelled residues reached a maximum of 56.3 ± 15.9 pmol ml 21 at 36 h and were still appreciable (13.3 ± 1.6 pmol ml 21 ) 30 d after treatment. Throughout the study period, total residue concentrations in bile (about 2-16 nmol ml 21 ), urine and faeces (0.5-3 nmol ml 21 or g 21 ) were higher than in other tissues sampled at slaughter. At slaughter there was evidence of residue accumulation in pigmented eye tissue (33.1 ± 6.1 pmol g 21 ) and in white (13.4 ± 3.4 pmol g 21 ) and black hair (28.9 ± 8.9 pmol g 21 ). Evaluation of radio-HPLC profiles of urine and bile extracts generally indicated that 19NT and 19NT laurate residues were present in relatively small amounts among a complex mixture of metabolites. GC-MS analysis of glucuronidase-hydrolysed bile extracts indicated that the major metabolites were 5b-estrane-3a,17a-diol, 5a-estrane-3b,17a-diol, 5a-estran-3a-ol-17-one (norandrosterone) and estra-1,3,5(10)-triene-3,17a-diol (17a-estradiol).

Role of Pyruvate Dehydrogenase Inhibition in the Development of Hypertrophy in the Hyperthyroid Rat Heart

“…In a previous study, nonoxidative glucose metabolism and glycogenolysis were observed to increase with hyperthyroidism. 37 The authors suggest that this was caused by a perturbation in energy metabolism, leading to increased levels of inorganic phosphate, which would stimulate glycogen metabolism.…”

“…In a previous study, nonoxidative glucose metabolism and glycogenolysis were observed to increase with hyperthyroidism. 37 The authors suggest that this was caused by a perturbation in energy metabolism, leading to increased levels of inorganic phosphate, which would stimulate glycogen metabolism.We also found evidence of increased anaplerotic processing of pyruvate, a mechanism by which carbon flux into the Krebs cycle can be maintained under conditions of reduced PDH flux. We have been able to identify and quantify an MRS resonance corresponding to [3-13 C]citrate, the formation of which has not previously been observed in vivo, in real time.…”

Analysis of 19-nortestosterone residue in animal tissues by ion-trap gas chromatography-tandem mass spectrometry

“…19-Nortestosterone (19-NT) was synthesized for the first time by Birch in 1950 and by Wilds andNelson in 1953 (Le Bizec et al, 2002;Kohler and Lambert, 2002), which is designed for treatments of a wide span of haematological, post surgical conditions, cachexia, and substitutive progestin supplementation, and is also used in veterinary as well as human medicine in case of protein deficiency, breast cancer, osteoporosis, or burns (Delbeke et al, 1995;Sauer et al, 1998;Bricout and Wright, 2004;Chen et al, 2004). In animal husbandry, 19-NT can enhance lean tissue growth, reduce fat deposition, increase the weight gain, and feed conversion efficiency (Roda et al, 2003;Conneely et al, 2007).…”

Preparation of monoclonal antibody based indirect competitive ELISA for detecting 19-nortestosterone residue

“…193 of the Ministry of Agriculture in April 2002). However, illegal use of NT as a growth promoter has been widely reported throughout Europe [2] and in China, thus prompting continuous surveillance to control its abuse.…”

“…In the 1950s, the recognition of the growth promoting property of NT led to it being used to accelerate meat production. It can enhance lean tissue growth, reduce fat deposition, increase the weight gain and feed conversion efficiency of animals [2][3][4]. Administration is usually by intramuscular injection of the esterified drug in suspension with benzyl alcohol and arachis oil, or inserted into the fleshy part of the ear.…”