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PubMed1983

Radioimmunoassay of the anabolic agent zeranol. II. Zeranol concentrations in urine of sheep and cattle implanted with zeranol (Ralgro).

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.

Animals↗
PubMed1986

Radioimmunoassay of the anabolic agent zeranol. III. Zeranol concentrations in the faeces of steers implanted with zeranol (Ralgro).

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.

Animals↗
PubMed1986

Radioimmunoassay of the anabolic agent zeranol. IV. The determination of zeranol concentrations in the edible tissues of cattle implanted with zeranol (Ralgro).

Rapid solvent extraction combined with a radioimmunoassay using a monoclonal antibody raised against a derivative of zeranol has been used to measure the residues of the anabolic agent zeranol in the edible tissues (muscle, liver, kidney and fat) of cattle treated with Ralgro. Calibration curves, both with and without, tissue extracts exhibit good parallelism. Regression analysis for the extraction of zeranol from tissues dosed with standard amounts of zeranol have correlation coefficients of 0.979, 0.991, 0.986 and 0.985 for muscle, liver, kidney and fat, respectively. The limits of decision defined as the mean value + 3 SD for the concentrations apparently observed (noise) in tissues from animals not treated with Ralgro were 278, 121, 373 and 110 ng/kg for muscle, fat, liver and kidney, respectively. In the tissues of 4 cows implanted with Ralgro (36 mg), and sampled 70 days after implanting, the highest concentration of zeranol in each tissue was 232 ng/kg (muscle), 391 ng/kg (liver), 287 ng/kg (kidney) and 293 ng/kg (fat), and residues were detected in all samples of fat (4), 3 kidney samples and 1 liver sample.

Adipose Tissue↗
PubMed2003

Interlaboratory ring test of time-resolved fluoroimmunoassays for zeranol and alpha-zearalenol and comparison with zeranol test kits.

Many zeranol immunoassay test kits cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the evaluation and application of recently published, dry reagent time-resolved fluoroimmunoassays (TR-FIA) for zeranol and the toxin alpha-zearalenol. A ring test of bovine urine fortified with zeranol and/or alpha-zearalenol in four European Union National Reference Laboratories demonstrated that the TR-FIA tests were accurate and robust. The alpha-zearalenol TR-FIA satisfactorily quantified alpha-zearalenol in urine fortified at 10-30 ng ml(-1). The specificity-enhanced zeranol TR-FIA accurately quantified zeranol in the range 2-5 ng ml(-1) and gave no false-positive results in blank urine, even in the presence of 30 ng ml(-1) alpha-zearalenol. Zeranol TR-FIA specificity was demonstrated further by analysing incurred zeranol-free urine samples containing natural Fusarium spp. toxins. The TR-FIA yielded no false-positive results in the presence of up to 22 ng ml(-1) toxins. The performance of four commercially available zeranol immunoassay test kits was more variable. Three kits produced many false-positive results. One kit produced only one potential false-positive using a protocol that was longer than that of the TR-FIA. These TR-FIAs will be valuable tools to develop inspection criteria to distinguish illegal zeranol abuse from contamination arising from in vivo metabolism of Fusarium spp. toxins.

Animals↗
PubMed1991

Determination of zeranol and beta-zearalanol in calf urine by immunoaffinity extraction and gas chromatography-mass spectrometry after repeated administration of zeranol.

A method for the determination of zeranol and its metabolite beta-zearalanol in bovine urine is described. It has been applied to samples from calves given multiple subcutaneous doses of zeranol. Samples were extracted with immunoaffinity columns containing antibodies raised against zeranol and were analysed by gas chromatography-mass spectrometry. The immunoaffinity columns were prepared by coupling immunoglobulin G fractions obtained from rabbit antisera with a Sepharose matrix. The immunizing agent was carboxybutylzeranol coupled to bovine serum albumin. Gas chromatography-mass spectrometry was performed in the negative-ion chemical ionization mode, after derivatization of the compounds to their pentafluorobenzyl ethers, and allowed detection of analytes with a sensitivity of 0.01 ppb in spiked urine. The derivatization method and the gas chromatographic determination were also applied to the similar compounds zearalanone, zearalenone and beta-zearalenol. A synthesis of dideuterated zeranol and beta-zearalanol by isotopic exchange is described. These deuterated analogues had an isotopic purity of more than 99% and were used for quantitation of zeranol and beta-zearalanol by isotope dilution mass spectrometry. The recoveries of zeranol and beta-zearalanol, using the immunoaffinity columns, were determined after extraction from spiked urine and were 84 and 64%, respectively. The urines of treated calves were collected for several days after treatments and were analysed after hydrolysis with beta-glucuronidase and arylsulphatase. The samples showed variable but generally decreasing concentrations of zeranol and beta-zearalanol. The levels of beta-zearalanol ranged from less than 0.01 to 98 ppb and were 1.2-3.2 times higher than those of zeranol.

Animals↗
PubMed2004

Prevalence of zeranol, taleranol and Fusarium spp. toxins in urine: implications for the control of zeranol abuse in the European Union.

There is currently little information concerning the prevalence of zeranol and taleranol in animal urine following metabolism of the naturally occurring Fusarium spp. toxins. An epidemiological study is described which involves four European Union control laboratories in which 8008 urine samples were screened for the presence of zeranol using a time-resolved fluoroimmunoassay (TR-FIA). Of these samples, 93.6% screened negative for zeranol. All samples testing positive for zeranol were then analysed with a confirmatory method. Based on the confirmatory results, the TR-FIA-positive samples were then categorized as false-positive, true-positive or 'equivocal' (zeranol/taleranol and the Fusarium spp. toxins detected). The true-positive samples represented only 0.05% of the total number of samples (n = 4). After statistical analysis, 170 of 174 equivocal samples proved to belong to a 'normal' population in which the amount of zeranol/taleranol could be related to the total amount of Fusarium spp. toxins through a linear regression with a 99% prediction interval. This suggested that the presence of zeranol in these samples might be due to in vivo metabolism of the Fusarium spp. toxins. The presence of zeranol in the four remaining 'outliers' might be attributable to zeranol abuse rather than to natural contamination. The results are of interest for control laboratories as they might provide an analytical tool to help distinguish between abuse and natural contamination in zeranol testing.

Animals↗
PubMed1986

Radioimmunoassay of the anabolic agent zeranol. V. Residues of zeranol in the edible tissues, urine, faeces and bile of steers treated with Ralgro.

Two trials were conducted on steers implanted with zeranol (Ralgro) to determine the edible tissue residues and the secretion pattern in faeces, urine and bile of zeranol residues throughout and beyond the recommended withdrawal period (70 days) for this drug. In the first trial there was considerable variation in the zeranol residue concentration in all edible tissues, the highest concentrations found in the liver being significantly above the control values (P less than 0.05). In the other tissues, only fat sampled 14 days after implanting was significantly above the control value (P less than 0.05). The zeranol concentration in bile samples obtained at slaughter [70 days (18), 90 days (5) and 120 days (2)] were all higher than the apparent concentration in the bile of untreated steers. The mean concentration of zeranol in the faeces and urine varied from day to day and between animals sampled on the same day following implantation. The highest mean concentrations were observed during the first 40 days following implanting, declining steadily to approach the control values 70 days after implantation. The second trial using steers prepared with bile duct re-entrant cannulae resulted in a similar pattern of zeranol excretion in bile, faeces and urine. The highest concentrations of zeranol were observed in bile and ranged from 24 to 34 micrograms/l; there was considerable variation between animals and within animals sampled on successive days. Although the concentration declined steadily, zeranol was still readily detectable 120 days after implanting.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed2002

Development and validation of dry reagent time-resolved fluoroimmunoassays for zeranol and alpha-zearalenol to assist in distinguishing zeranol abuse from Fusarium spp. toxin contamination in bovine urine.

Zeranol, an oestrogenic growth promoter in food animals, is banned within the European Union (EU). However, commercially available immunoassay kits for zeranol cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the validation of a specificity enhanced, rapid dry reagent time-resolved fluoroimmunoassay (TR-FIA) for zeranol (recovery 99%, limit of detection 1.3 ng ml(-1)) demonstrating that up to 150 ng ml(-1) of Fusarium spp. toxins in urine do not lead to false-positive results. This assay will assist EU Member States to implement Council Directive 96/23/EC, which requires states to monitor for potential abuses of zeranol. A similar TR-FIA for the Fusarium spp. toxin alpha-zearalenol, using the same sample extract, is also described (recovery 68%, limit of detection 5.6 ng ml(-1)). Only the addition of diluted sample extract is required to perform these dry-reagent TRFIAs, the results being available within 1h of extract application. The EU-funded project 'Natural Zeranol' (FAIR5-CT97-3443) will use these fluoroimmunoassays to screen bovine urine in four Member States to gather data on the seasonality of Fusarium spp. toxin contamination of urine and the incidence of zeranol screening test positives.

Animals↗
PubMed1993

Measurement of zeranol in plasma from three blood vessels in steers implanted with zeranol.

Zeranol (Z) is a widely used growth promotant; however, plasma Z profiles in cattle implanted with Z have not been characterized. This study was conducted to determine bovine plasma Z profiles. In Exp. 1, four steers (BW = 284.8 +/- 5.6 kg) were implanted with 108 mg of Z (Ralgro). To determine the effect of sampling site on plasma Z concentrations, blood was sampled by venipuncture from the maxillary vein ipsilateral (IMV) to the ear in which Z was implanted and from the ipsilateral (IJV) and contralateral (CJV) jugular veins of each steer. Samples were collected on d 1, 4, 6, 8, 11, and 13 after implantation and Z was assayed by RIA. There was an effect of sampling site (P < .01). The overall mean plasma Z concentrations and 95% confidence intervals (CI) for each vessel were 282 (CI: 172 to 463), 135 (CI: 85 to 215), and 67 (CI: 42 to 106) pg/mL for the IMV, IJV, and CJV, respectively. Plasma Z concentration was higher (P < .05) in IMV than in IJV and higher (P < .05) in IJV than in CJV. In Exp. 2, nine steers (BW = 316.7 +/- 10.0 kg) were implanted with 108 mg of Z and IMV blood was collected on d 0, 1, 3, 7, 10, 14, 17, 21, 28, 35, 42, 56, 63, 73, and 91 after implantation. Day affected plasma Z concentration (P < .01); plasma Z was elevated above preimplantation levels for 91 d (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Effect of zeranol or melengestrol acetate (MGA) on testicular and antler development and aggression in farmed fallow bucks.

Fifteen yearling fallow bucks were randomly assigned by BW to one of three treatment groups: control (C; n = 5), melengestrol acetate (MGA; n = 5), and zeranol (Z; n = 5), to evaluate effects on testicular development, aggressive behavior, antler growth, sexual activity, ADG, and BW. Zeranol-treated bucks received zeranol ear implants (36 mg) at 90-d intervals, and MGA-treated bucks received MGA in the ration (100 microg x animal(-1) x d(-1)). Bucks grazed ryegrass/Coastal bermudagrass pasture and were supplemented with 3:1 corn/soybean meal at 0.45 kg x animal(-1) x d(-1). Body weights, body condition scores (BCS), blood samples, and testis measurements were obtained at d 0 and at 14-d intervals for 229 d. As bucks reached hard antler (7/15 to 8/25), antlers were harvested and weighed, and ejaculates were collected at 14-d intervals. Aggression was evaluated using 10-min video sessions scoring body blows, avoidance, head pushes, and head bunts. Scrotal circumference (SC) and paired testis volume were affected by a day x treatment interaction (P < 0.01); testes of zeranol-treated bucks were smaller than those of control or MGA-treated bucks. First sperm in the ejaculate tended to be delayed (P < 0.10) in zeranol-treated bucks compared with control and MGA-treated bucks. Melengestrol acetate-treated bucks had a maximum sperm concentration in the ejaculate that was three times (P < 0.05) that of control bucks and nine times (P < 0.05) that of zeranol-treated bucks. Antler weight was the least (P < 0.01) for bucks receiving zeranol and greatest (P < 0.10) for MGA-treated bucks; intermediate values were recorded for the control bucks. Aggressive behavior was delayed (P < 0.05) for zeranol-treated bucks until treatment effects were overcome. Melengestrol acetate-treated bucks had decreased (P < 0.01) aggressive behavior compared with control bucks. Melengestrol acetate-treated bucks had increased (P < 0.05) serum testosterone concentrations compared with control and zeranol-treated bucks. Human chorionic gonadotropin-stimulated peak serum testosterone concentrations for zeranol-treated bucks were delayed (P < 0.01) compared with control and MGA-treated bucks. Although zeranol-treated bucks overcame treatment effects, they were never able to reach testicular measurements or sperm concentrations equal to those of the control or MGA-treated bucks. Zeranol and MGA treatments may have both positive and negative effects that can be utilized when producing slaughter bucks.

Aggression↗
PubMedDate not supplied

Zeranol is formed from Fusarium spp. toxins in cattle in vivo.

Zeranol, a semi-synthetic oestrogenic growth promoter, was banned in the EU in 1988. The ability of Member States to police the ban on zeranol has been hampered by suggestions from New Zealand and from this laboratory that zeranol may be formed by the in vivo metabolism of naturally occurring Fusarium spp. toxins. The present study demonstrates that zeranol is formed from alpha-zearalenol and zearalenone in vivo and is detected in bovine bile following the oral administration of these compounds. However, it is not detected following administration of beta-zearalenol. These data suggest that hydrogenation of alpha-zearalenol, probably in the rumen, is responsible for the appearance of zeranol. The present study shows that environmental contamination with Fusarium spp. toxins is widespread in Northern Ireland. Fusarium spp. toxins were present in 32% (n = 422) of all bovine bile samples tested for zeranol during 1995. Zeranol itself was confirmed in 6.6% (n = 28) of the samples. However, the mean alpha-zearalenol and beta-zearalenol concentrations in the bile of zeranol-positive animals were 12 and 9 times higher, respectively, than those in the zeranol-negative animals. The alpha-zearalenol concentration always exceeded the zeranol concentration by at least 5:1. This may, in the future, permit differentiation between zeranol abuse and natural contamination.

Animals↗
PubMed1986

Effects of zeranol and trenbolone acetate on testis function, live weight gain and carcass traits of bulls.

The ability of zeranol and trenbolone acetate (trenbolone) to alter testis function, weight gain and carcass traits of young bulls was studied. In Exp. 1, the effects of age at initial zeranol implantation was determined. After a 235-d experimental period, sequential implantation (56-d intervals) beginning at 100 or 150 d of age had reduced testis growth (P less than .01), sperm production (P less than .01) and serum testosterone concentration in response to gonadotropin releasing hormone (GnRH; P less than .01). The 200-d age group was partially suppressed, while the 250-d age group was not affected. Body weights were similar to controls in all groups. In Exp. 2, bulls previously implanted with zeranol at 175 and 231 d of age received single implants of zeranol, trenbolone or trenbolone plus zeranol at approximately 300 d of age. At slaughter (135 d later), body weight and carcass characteristics in all treatments were similar to controls. However, trenbolone reduced sperm production (P less than .05), zeranol reduced sperm production and testes weight (P less than .05), but trenbolone plus zeranol was similar to controls. Mean testosterone response to GnRH was suppressed in all implant groups on d 65 (P less than .01), but only in trenbolone or trenbolone plus zeranol groups on d 112 (P less than .05). Results indicate that zeranol suppresses spermatogenesis and testosterone production if implanted before approximately 200 d of age. Reduction of endogenous testosterone without alteration of weight gain or carcass characteristics may be of benefit if behavioral or masculinity traits of bulls are altered. Also, it appears that no benefit is derived from implanting bulls with both trenbolone and zeranol.

Animals↗
PubMed1983

Acute and chronic changes in adenohypophyseal hormone secretion in sheep during zeranol administration.

The effect of zeranol on circulating plasma concentrations of 5 adenohypophyseal (anterior pituitary gland) hormones was investigated in growing, castrated male sheep in 3 studies: after IM injection of 1 mg of zeranol (acute study), during a 6-week period after subcutaneous implantation of 12 mg of zeranol (chronic study), and during a 4-hour continuous IV infusion of gonadotropin-releasing hormone (Gn-RH) plus thyrotropin releasing hormone (TRH), 10 micrograms/hour. The sheep used in the chronic study (challenge study) were the same animals used in the 6-week implant study. Plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), thyroid-stimulating hormone (TSH), and growth hormone (GH) were measured by specific radioimmunoassay. Injection of zeranol resulted in a transient decrease in circulating LH and prolonged reduction in FSH concentrations during the 24-hour sampling period. Plasma concentrations of PRL, TSH, and GH in zeranol-injected and control animals were not different. Implantation of zeranol caused chronic reduction in plasma LH and FSH, an increase in PRL, and no change in plasma GH or TSH concentrations compared with values for control animals. In the challenge study, IV infusion of Gn-RH and TRH caused a significant increase in the concentration of each of the 5 hormones compared with preinfusion values, regardless of zeranol treatment. When the hormone-response profiles were compared between zeranol-treated and control sheep in this challenge study, only the LH response was different--being greater in zeranol-treated sheep. Generally, the administration of zeranol resulted in a more pronounced alteration in basal and stimulated secretion of reproductive hormones such as LH, FSH, and PRL than in GH or TSH, which are more commonly associated with growth and development.

Animals↗
PubMed1993

Effects of different doses of zeranol on growth, hemoglobin, and carcass traits in veal calves.

Effects of different doses of zeranol on ADG, hemoglobin (Hb), feed efficiency (FE), and carcass traits were evaluated in special-fed veal calves in two trials. On d 0, calves were implanted subcutaneously in the middle third of the ear with either 0 (control, placebo pellet), 12, 24, 36, or 48 mg of zeranol. Trial 1 was conducted from February through May 1990 with 120 Holstein bull calves (17 to 21 d of age on d 0) and Trial 2 was conducted from May through August 1991 with 100 Holstein bull calves (24 to 28 d of age d 0). Calves were fed on an individual calf basis. Calves in Trial 1 that were implanted with 48 mg of zeranol had improved FE (P < .05) and ADG (P < .05) during Period 1 (0 to 43 d). No significant differences in ADG or FE were observed among treatments in Trial 2. Hemoglobin levels at slaughter averaged 7.88 +/- .096 and 8.19 +/- .149 g/dL over all treatments for Trials 1 and 2, respectively. The only postslaughter trait affected by zeranol dose was testicular weight. In both trials, testicular weight at slaughter decreased (P < .05) with increasing doses of zeranol. Dressing percentage tended to be higher for 48-mg implants than for controls but the difference was not significant. There were no significant zeranol dose effects on longissimus muscle area, flank color, carcass conformation, or percentage of fore- vs hind-quarter weight. These results indicated that higher doses of zeranol improved ADG and FE during the first 6 wk after the trial period (to 8 wk of age), decreased testicular weight, and increased hide-on carcass dressing percentage for calves implanted with 48 mg of zeranol compared with those that received 0 mg of zeranol.

Animals↗
PubMedDate not supplied

Effects of prepubertal zeranol exposure on estrogen target organs and N-methyl-N-nitrosourea-induced mammary tumorigenesis in female Sprague-Dawley rats.

BACKGROUND: There are no previous reports of the effects of prepubertal exposure to zeranol, an estrogenic substance, on estrogen-responsive reproductive organs and mammary glands in rats, or its effects on N-methyl-N-nitrosourea (MNU)-induced mammary tumorigenesis in rats. MATERIALS AND METHODS: Prepubertal female Sprague-Dawley rats were treated daily with either 0, 0.1 or 10 mg/kg body weight of zeranol between 15 and 19 days of age. They were given 50 mg/kg body weight MNU at 28 days of age, and were monitored for occurrence of mammary tumors > or = 1 cm in diameter. Body weight gain, structures and functions of estrogen target tissues, and mammary carcinogenesis were compared between dosage groups. RESULTS: Zeranol did not affect body weight gain. At 28 days of age, zeranol-treated and -untreated rats showed similar development of reproductive organs and mammary glands. However, both low- and high-dose zeranol treatment caused significantly earlier vaginal opening, irregularity of estrous cycle (high frequency of prolonged estrous or prolonged diestrous) at 8 to 11 weeks of age, and anovulatory ovary (ovaries without newly formed corpora lutea). At 37 weeks of age, the high-dose zeranol-treated group exhibited increased relative uterine-ovarian weight, but mammary gland development was comparable to that of untreated rats. Mammary carcinogenesis was not affected by low- or high-dose zeranol treatment. CONCLUSION: Short-duration zeranol treatment in the prepubertal period severely damaged ovarian functions and structure, but mammary carcinogenesis was not affected. The present results suggest that ingestion of foods containing zeranol in the infantile period can cause dramatic endocrine disruption in later life.

Animals↗
PubMed1993

Improved thin-layer chromatographic detection of diethylstilbestrol and zeranol in plasma and tissues isolated with alumina and ion-exchange membrane columns in tandem.

Clean-up procedures for the isolation of zeranol and diethylstilbestrol (DES) were modified to reduce the analysis time and to increase the efficiency of purification. Several dyes (Fast Blue BB, Fast Corinth V, Fast Blue RR, Fast Blue B, Fast Red Violet B and Fast Violet B) were evaluated, and their minimum detectabilities were determined. Conditions for non-instrumental, semi-quantitative thin-layer chromatography were optimized. Zeranol and DES in plasma and tissues were determined using modified procedures. Enzyme digestion brought about significant improvement in detectabilities of zeranol and DES in both fortified and incurred plasma, serum and tissues. Minimum detectabilities for zeranol and DES were 25 ppb in fortified plasma and tissues. The amount of incurred zeranol measured in the serum of an experimental cow was increased four times, i.e. from 50 to 200 ppb, after protease digestion. Glucuronidase digestion showed an eight-fold increase in detection of incurred zeranol levels in bovine liver eight times. These results suggest that digestion releases zeranol and DES from protein and glucuronide complexes, thereby allowing detection of low levels of zeranol and DES which may not be detectable without digestion. Further modification of the purification with an ion-exchange membrane reduced the analysis time by 25%, and the membranes were regenerated up to ten times without loss of activity, allowing an automated process. This method utilizes inexpensive equipment and avoids use of organic solvent, in this case diethyl ether.

Aluminum Oxide↗
PubMed2001

Oestrogenic potencies of Zeranol, oestradiol, diethylstilboestrol, Bisphenol-A and genistein: implications for exposure assessment of potential endocrine disrupters.

We have compared the oestrogenic potency of the synthetic oestrogen Zeranol, used as a growth promoter in meat production, and five related compounds, with the potency of 17beta-oestradiol, diethylstilboestrol (DES), genistein, and Bisphenol-A. The potency was assayed by analysing differences in expression levels of endogenous oestrogen-regulated genes in human MCF7 cells, treated with different concentrations of the compounds. Zeranol, 17beta-oestradiol and DES were about equally potent, genistein was four to six orders of magnitude less potent than 17beta-oestradiol but an order of magnitude more potent than Bisphenol-A. There were gene specific differences, the PS2 and TGFbeta3 genes were about equally sensitive to Zeranol, 17beta-oestradiol and DES whereas a down-regulation of MRG1/p35srj could be detected at fmol/l concentrations of Zeranol whereas 17beta-oestradiol was several orders of magnitude less potent. GST mu3 was sensitive to fmol/l concentrations of 17beta-oestradiol but much less sensitive to Zeranol and DES. The very high potency of Zeranol compared with other potential endocrine disrupters suggests that Zeranol intake from beef products could have greater impact on consumers than the amounts of the known or suspected endocrine disrupters that have been found in food. Since little data is available in man, there is an urgent need for reliable measurements of the concentration of Zeranol in human serum after ingestion of meat products from treated animals.

Amino Acid Transport Systems, Basic↗
PubMed1995

Influence of incremental zeranol implant doses on the chemical and physical characteristics of third metacarpal bone and chemical composition of liver and soft tissue from feedlot steers.

Chemical and physical characteristics of third metacarpal bones and liver and rib soft tissue composition from feedlot steers were determined. Steers were selected (32 from each experimental location) to represent the range in slaughter weight and composition for each treatment group in three (total n = 1,088) feedlot experiments. Steers were implanted with 0, 24, 36, 48, 60, 72, 84, or 96 mg of zeranol at approximately 140 d before slaughter. Cattle at each location were fed for the same number of days and slaughtered as a group. Zeranol dose had no effect on the chemical composition of bone, liver, or rib soft tissue with the following exceptions: zeranol decreased (P < .01) bone Ca concentration and increased (P < .07) liver P concentration. Zeranol implantation decreased medullary cavity anterioposterior (AP) diameters and AP cortical width (P < .08). Loads withstood by the bones up to flexure (P < .08) and the strain at flexure (P < .09) were inversely related to the quadratic of zeranol dose. However, modulus of elasticity at flexure and breaking increased numerically with zeranol dose. Stress withstood by bones at flexure was greater (P < .09) for implanted steers. Strain data indicate that metacarpals from steers receiving zeranol would exhibit less deformation upon loading to flexure (P < .09) than controls. These data indicate that administration of intermediate doses of zeranol altered bone deposition of Ca, which resulted in modified third metacarpal physical and mechanical characteristics.

Animals↗