Beta2-agonist abuse in food producing animals: use of in vitro liver preparations to assess biotransformation and potential target residues for surveillance.
1. The biotransformation of [3H]clenbuterol, [3H]salbutamol, [14C]salmeterol and 7-ethoxycoumarin by bovine liver was investigated by incubation with freshly prepared microsomes, suspension and monolayer cultures of isolated hepatocytes, precision-cut (250 microm) and chopped (600 microm) tissue slices. 2. Radio-HPLC analysis indicated that the saligenin beta2-agonists salmeterol and salbutamol were extensively metabolized by all intact cell preparations. A single major product (SmM1) was evident for salmeterol and two unresolved products for salbutamol (SbM1 and SbM2). Differential enzyme hydrolysis studies with Helix pomatia beta-glucuronidase/aryl sulphatase indicated that the main metabolites were glucuronide conjugates. Consistent with this, analysis of metabolites by liquid chromatography-mass spectrometry showed molecular ions ([M+H]+) at m/z 592 for Sm1 and 416 for both Sb1 and Sb2. 3. Comparable studies with clenbuterol revealed three minor metabolites. Prolonged incubations generated products representing, at maximum, 27% biotransformation. Two of the products have been identified as a glucuronide ([M+H]+, m/z 453) and hydroxyclenbuterol ([M+H]+, m/z 293). 4. These findings indicate that in vitro studies provide simple and cost-effective means of evaluating xenobiotic metabolism, and thus of identifying potential target residues to enable surveillance of use of unlicensed veterinary drugs, or prohibited substances in farm animals.
Sauer
M J
MJ
Risk Research Department, Veterinary Laboratories Agency, New Haw, Addlestone, UK. m.j.sauer@vla.maff.gov.uk
Dave
M
M
Lake
B G
BG
Manchee
G R
GR
Howells
L C
LC
Coldham
N G
NG
D000318:Adrenergic beta-Agonists / Q000032:analysis* / Q000378:metabolism / Q000493:pharmacokinetics*; D000420:Albuterol / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D000818:Animals; D001711:Biotransformation; D002417:Cattle; D002976:Clenbuterol / Q000032:analysis / Q000378:metabolism; D003374:Coumarins / Q000378:metabolism; D005506:Food Contamination / Q000517:prevention & control; D005517:Foodborne Diseases / Q000378:metabolism; D008099:Liver / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008461:Meat Products; D008862:Microsomes, Liver / Q000737:chemistry / Q000378:metabolism; D000068299:Salmeterol Xinafoate
D000318:Adrenergic beta-Agonists; D003374:Coumarins; C017299:7-ethoxycoumarin; D000068299:Salmeterol Xinafoate; D000420:Albuterol; D002976:Clenbuterol