Accumulation of the beta(2)-adrenergic agonist clenbuterol in mouse dark hair.

The aim of the present study was to evaluate the suitability of dark hair as a matrix for determination of the beta(2)-adrenergic agonist clenbuterol residues using previously validated enzyme-linked immunosorbent assay (ELISA) as a screening method for its quantitative determination. The experimental group of mice (n = 60) were treated with two different anabolic dosages of clenbuterol for 15 days, whereas the control group of animals (n = 30) was left completely untreated. Hair samples were collected on days 0, 5, 10, and 15 of treatment. Validation of the ELISA analytical procedure showed good recovery (mean recovery 74%) with an acceptable intra-assay variation in individual measurements for all hair samples to which 5, 10, and 50 ng/g clenbuterol were added (CV < 10%). Low blank levels of clenbuterol (2.4 +/- 0.6 ng/g) were measured in hair of untreated mice, whereas significantly higher clenbuterol concentrations rising proportionally with the time of treatment were recorded in hair of mice treated with lower (6.5 mg/kg body mass) and higher (12.5 mg/kg body mass) dose of clenbuterol. The peak hair concentration of clenbuterol measured on the last day of treatment (day 15) was 1553.9 +/- 140.1 ng/g and 6248.3 +/- 589.4 ng/g in the lower and higher dose group, respectively. Study results clearly indicated dark hair as a pigmented tissue to have a high accumulation potential for clenbuterol residues, thus being the target matrix of choice for detection of clenbuterol abuse as an anabolic in meat production.

Xenobiotic clenbuterol in food producing male pigs: Various tissue residue accumulation on days after withdrawal.

Using enzyme-linked immunosorbent assay (ELISA) and liquid chromatography tandem mass spectrometry (LC-MS/MS) the concentrations of clenbuterol (ng/g) were shown to be highest in choroid/pigmented retinal epithelium (choroid/PRE) (499.59±26.36ng/g), followed by hair (fair colored) (207.76±86.88ng/g), liver (25.06±16.72ng/g) and kidney (6.88±3.52ng/g) after 28 days of oral clenbuterol administration in a growth-promoting dose (10µg/kg BW, twice daily) to food producing male pigs, with a high correlation coefficient between the two methods for all study matrices (r=0.8800-0.9999). In the liver as an alimentary tissue and regulatory matrix for the control of clenbuterol abuse, the maximal allowed concentration of 0.5ng/g was achieved in liver tissue (0.40±0.12ng/g) on day 14 and in the kidney (0.28±0.10ng/g) on day 7 after treatment withdrawal. In contrast, the concentration of residual clenbuterol in choroid/PRE (57.49±6.13ng/g) and hair (68.36±3.35ng/g) recorded on day 14 of withdrawal was 143- and 170-fold that measured in the liver, with a similar ratio persisting on day 35 of withdrawal (164:1 and 183:1, respectively). These findings indicated a high accumulation potential of clenbuterol residues in the hair and choroid/PRE as compared with the liver and kidney, pointing to the pig choroid/PRE and hair as useful new matrices in the control of clenbuterol abuse as a growth promotant in food production, especially after prolonged withdrawal.

Serum luteinizing hormone response to administration of gonadotropin-releasing hormone to atrazine-treated gilts.

The aim of the study was to evaluate the response of porcine luteinizing hormone (pLH) in serum to a single iv administration of gonadotropin-releasing hormone (GnRH) in atrazine-treated pigs. Experiments were performed in 15 mature female pigs (10 atrazine-treated, 5 control). From the onset of estrous (day 0), the pigs were given 1 mg atrazine/kg body mass in feed for 20 d of the estrous cycle. On the last day, blood samples were collected at min 0 from control and atrazine-exposed, and 5 atrazine-exposed pigs were immediatey given 100 mg GnRH iv. Blood samples were collected from atrazine-exposed and the GnRH-injected atrazine-exposed groups at 20, 30, 40 and 90 min and serum pLH concentrations were determined by radioimmunoassay. The administration of atrazine led to significant (p< 0.001) suppression of serum pLH concentrations (0.57 +/- 0.05 ng/ml) compared to control animals (2.24 +/- 0.20 ng/ml). The single iv GnRH administration to the atrazine-exposed pigs provoked significant pLH release at 20 and 30 min after GnRH administration, indicating attenuation of GnRH release in the atrazine-exposed animals was responsible for the suppression of serum pLH.

Effects of repeated growth-promoting doses of clenbuterol on the hepatic function of female pigs.

The effect of repeated administration of clenbuterol in a growth-promoting dose on hepatocellular integrity of female pigs was assessed by correlating histopathologic lesions in the livers of dosed pigs with changes in serum ALT, AST, GGT and AP activities. The experiments were carried out in 12 (6 control and 6 treated) female pigs (Fl generation Swedish Landrace and Large Yorkshire) 6-7 mo and 80-100 kg bw. Experimental animals were treated with 10 microg clenbuterol/kg bw iv twice daily for 25 d prior to being sacrificed. Blood and liver samples were collected. Treated animals had increased serum AP and ALT activities (p< 0.02), whereas serum AST and GGT activities did not significantly change. Mild hyperplasia of biliary ducts, interstitial liver inflammation and hydropic and vacuolar hepatocyte degeneration were observed. These findings indicate that repeated administration of growth-promoting doses of clenbuterol to female pigs adversely affect liver function.