No abstract

A pharmacokinetic study is described in which Friesian calves (n = 30) were treated orally with clenbuterol at 10 times the therapeutic dose. The study was designed to establish the distribution and elimination of clenbuterol from edible tissues, the major compartments of the eye and body fluids. Animals (n = 24) were dosed (10 micrograms/kg body weight) twice daily with clenbuterol for 21 days and slaughtered in groups of five (one untreated control animal per group) at 6 h and 1, 2, 4, 8 and 16 days after cessation of treatment. At slaughter, samples of diaphragm muscle, liver, kidney, bile, urine and both eyes were obtained. One of the eyes was separated into constituent tissues: aqueous humour, vitreous humour, cornea, lens, retina (without pigmented epithelium), choroid (with pigmented retinal epithelium; choroid/PRE) and sclera. All samples were stored at -20 degrees C. Clenbuterol concentrations were higher in liver than kidney, bile and urine from day 2 of withdrawal onwards. Concentrations in choroid/PRE were at least 10 times higher than in liver at all periods following cessation of treatment and 52 times higher 16 days after treatment. The concentrations of clenbuterol in the constituent tissues of the eye were in the order choroid/PRE > cornea > > retina > aqueous humour/vitreous humour > or = lens. Concentrations of clenbuterol in choroid/PRE taken from eyes frozen whole were generally lower than those in choroid/PRE separated before storage. Choroid/PRE stored by either method contained clenbuterol at more than 100 ng/g 16 days following cessation of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

A radioimmunoassay for zeranol has been validated and used to measure the concentration of zeranol in the urine of sheep and cattle treated with zeranol (Ralgro). The assay uses an antibody raised against zeranol-16-carboxy-propyl ether conjugated to human serum albumin. In sheep and cattle urine the limits of detection were approximately 2 ng/ml and 2.5 ng/ml, respectively. In two trials 13 sheep were implanted with 12 mg zeranol at the base of the ear. The mean maximum concentrations of zeranol observed in urine were 45 ng/ml (Trial I) on day 35 and 90 ng/ml (Trial II) on day 56, and had declined to 26 ng/ml 42 days after implantation (Trial I) and 11.7 ng/ml 70 days after implantation (Trial II). In four cattle implanted with 36 mg zeranol the concentrations of zeranol in urine reached a mean maximum concentration of 13.5 ng/ml 22 days after implantation and had declined to 2.9 ng/ml 69 days after implantation.

Summary. Cows of normal reproductive history were treated with progesterone for periods of 2\p=n-\3months. The uterine secretions yielded 5 major fractions of macromolecular components. Two of the fractions comprised serum proteins. In the other 3 fractions at least 9 non-serum proteins were observed, 7 in one fraction, but in only small amounts. Of the remaining 2 non-serum proteins one is an acid phosphatase recoverable in small amounts, and the other is lactoferrin and is the major non-serum protein present in the uterine secretions of progesterone-treated cows.

Using a monoclonal antibody raised against zeranol, a radioimmunoassay has been validated for the determination of zeranol residues in the faeces of treated steers. The limit of decision defined as the mean apparent concentration of zeranol in the faeces of untreated cattle + 3 SD was 1 ng/g faeces. In a trial in which 27 steers were implanted with zeranol (36 mg) at the base of the ear and six steers were sham implanted, the mean maximum concentration of zeranol in faeces was 5.8 ng/g on Day 15 following implanting, declining to 1.67 ng/g on Day 34 following implanting. During this period there was a marked variation between animals sampled on the same day following implanting. At no time during the trial did the apparent concentration of zeranol in the faeces of untreated animals rise above 0.91 ng/g, which is below the limit of decision for this assay.