Development of a specific radioimmunoassay for the detection of clenbuterol residues in treated cattle.

A radioimmunoassay for clenbuterol detection in cattle has been validated and used to monitor treated cattle. The tracer used was 4-amino-3,5-dichloro-alpha(tert-butylamino-methyl) benzyl alcohol (benzyl-3H)(clenbuterol) prepared by catalytic tritiation with tritium gas of 4-amino-3,5-dibromo-alpha-(tert-butylamino)-acetophenone, followed by chlorination at positions 3 and 5 in the aromatic ring. The rabbit antiserum was raised against a diazotized clenbuterol/human serum albumin conjugate. The assay described was sensitive (7.8 pg/tube) and reproducible. The intra- and inter-assay variability, which was assessed by measuring known quantities of clenbuterol in plasma, urine and faeces, was satisfactory for RIA. When this assay was used to monitor treated cattle the concentrations of clenbuterol in plasma, urine and faeces were directly related to the administered dose. The absorption and elimination of clenbuterol in cattle was rapid. Data obtained were consistent with results obtained in other species where a rapid clearance rate was also demonstrated.

Reproductive performance of dibromochloropropane-treated female rats.

Dibromochloropropane (DBCP) is an effective nematocide which has been shown to suppress spermatogenesis and cause infertility in both men and male rats. There are no similar reports concerning the effects of DBCP on female reproduction. The purpose of the present study was to attempt to interfere with the various phases of oogenesis. Proestral or pregnant rats were injected subcutaneously once with 40 mg/kg DBCP on one of each days of L12-L20 of gestation; a double dose (80 mg/kg) was injected in eight consecutive days (L11-L18). In addition, L13 fetuses were injected--directly into the amniotic sac--with 0.1 mg DBCP. Pooled data from the various days of gestation revealed that postimplantation losses were three times as high in the DBCP-treated animals as in DMSO-treated controls. Perinatal deaths were 58% higher and mean pup weights were 30% lower in the DBCP-treated rats than in controls. The reproductive performance of females exposed to DBCP while in utero was affected only to a limited degree (reduced number of ovulations and implantations) as compared with their DMSO counterparts. Doubling the dose (80 mg/kg) seriously reduced the birth weight of pups (50% of controls), all of which died within several hours post-partum. Direct injection of DBCP into embryos or to proestral rats did not have any adverse effects on their future reproductive performance. In contrast to the effect on spermatogenesis, it appears that oogenesis and ova are unaffected by DBCP.

Gonadotoxicity and kinetics of dibromochloropropane in male rats.

Adult male rats were injected with [3H]dibromochloropropane dissolved in dimethylsulfoxide containing about 10 X 10(6) dpm. Blood from the tail and 24-h urine samples were collected up to 2 days post-injection. Tissue samples were further taken from the kidneys, liver, spleen, adrenals, epididymis, seminal vesicles and testes 7 h and 7 days post-injection. The results demonstrate that there is no preference in labelling of the testes compared with other organs, and the kidney and liver may have an important role in the elimination of DBCP.

Dopamine D2 receptors selectively labeled by a benzamide neuroleptic: [3H]-YM-09151-2.

In order to label dopamine D2 receptors selectively we tritiated the potent benzamide neuroleptic, YM-09151-2 (26.7 Ci/mmol). The binding of [3H]-YM-09151-2 to canine striatal membranes was saturable and specific with a KD of 57 pmol/l and Bmax of 36 pmol/g tissue as determined by Scatchard analysis. The KD, but not the Bmax, of [3H]-YM-09151-2 increased 6-fold in the absence of sodium chloride. [3H]-YM-09151-2 labeled 40% more sites than [3H]-spiperone in the same tissue homogenate. [3H]-YM-09151-2 binding was inhibited by dopaminergic drugs in a concentration and stereoselective manner with the appropriate dopamine D2 receptor profile. Thus, dopamine agonists inhibited [3H]-YM-09151-2 binding to canine striatal membranes with the following rank order of potency: (-)-N-n-propylnorapomorphine greater than apomorphine greater than (+/-)-6,7-dihydroxy-2-aminotetralin greater than (+)-N-n-propylnorapomorphine greater than dopamine greater than (-)-noradrenaline greater than serotonin greater than (-)-isoprenaline. Dopaminergic antagonists competed for [3H]-YM-09151-2 binding with the following order of potency: spiperone greater than (+)-butaclamol greater than haloperidol greater than clebopride greater than (-)-sulpiride greater than SCH-23390 greater than (-)-butaclamol. Furthermore, dopamine agonists recognized 2 states of the receptor labeled by [3H]-YM-09151-2, Dhigh2 and Dlow2. The Dhigh2 state of the receptor could be converted to Dlow2 by guanine nucleotides and sodium ions as is the case for [3H]-spiperone binding to D2 receptors. [3H]-YM-09151-2 appears to be a more selective ligand for dopamine D2 receptors than [3H]-spiperone, since YM-09151-2 displays approximately 9-fold lower affinity than spiperone for cortical serotonergic (S2) receptors. [3H]-YM-09151-2 may become a useful tool for the selective characterization of dopamine D2 receptors.

Structure assignment by retention index in gas-liquid radiochromatography of substituted cyclohexenes.

Substituents and functional groups cause increase in retention indexes of six-membered ring compounds on apolar and polar columns. These retention index increments (delta I) are characteristic and structure-dependent showing a structure-retention index relationship. The delta I values obtained for methyl and halogen atom substitution, cyclohexenes, and cyclohexanes are useful for predictive purpose in tritium labeling studies for tentative structure assignment of radioactive intermediates not amenable to analysis by conventional techniques.