Rapid immunoassay method for the determination of clenbuterol and salbutamol in blood.

The aim of the study was to evaluate the adequacy of enzyme-linked immunosorbent assay (ELISA) in the post-exposure determination of the ß-agonists clenbuterol and salbutamol in animal plasma and serum. Experimental guinea pigs (n = 20) were treated with two doses (0.25 and 2.5 mg/kg) of clenbuterol (n = 10) and salbutamol (n = 10) for seven days, whereas the control animal group (n = 10) was left untreated. Validation of the applied method yielded acceptable recovery (mean > 70%) and repeatability rates, showing ELISA to be applicable for the semi-quantitative determination of both analytes in both matrices, preferably in plasma. In both matrices, clenbuterol concentrations were proven to be significantly (14-fold) higher than those of salbutamol. Concentrations of both analytes were higher in plasma than in serum. The application of a 10-fold higher clenbuterol and salbutamol dose (2.5 mg/kg) resulted in concentrations 3- to 4-fold higher for clenbuterol and 2- to 3-fold higher for salbutamol, indicating a different release rate of these two ß-agonists.

Comparison of ractopamine residue depletion from internal tissues.

The aim of the study was to compare residue depletion of ractopamine HCl as a ß-adrenergic agonist that promotes muscle growth of animals, from internal tissues on days after its repeat administration to animals. The experiment was carried out in 38 albino guinea pigs. Treated animals (n = 30) were orally administered ractopamine HCl in a dose of 3.5 mg/kg body mass per day for 7 consecutive days. On days 1, 10, 20 and 30 of drug discontinuation, animals were randomly sacrificed and the liver, kidney, lung, heart, muscle, spleen and fat samples were collected. In all matrices, ractopamine concentration was determined using validated enzyme-linked immunosorbent assay (ELISA) as a quantitative screening method. The highest ractopamine concentration was recorded on day 1 in the lungs (55.80 ± 15.62 µg/kg), followed by the kidney (21.85 ± 3.91 µg/kg), spleen (12.59 ± 1.95 µg/kg), fat (10.17 ± 5.02 µg/kg), heart (9.73 ± 0.22 µg/kg), liver (5.58 ± 2.09 µg/kg), and lowest in muscle (2.21 ± 1.02 µg/kg). Ractopamine residues were detected in the lungs in the period of 30 days after withdrawal in significantly higher concentrations in comparison to other investigated matrices, suggesting that depletion of ractopamine from the lungs occurs at a much slower rate than its depletion from other internal tissues.