Total Radioactive Residues Research Articles

Analysis of Tissue Residues and Comparative Metabolism of Ardacin in Cattle, Broilers, and Rats

Following continuous administration, ardacin residues equilibrated in tissues of cattle and broilers after 13 and 22 days, respectively, with average total residues of <111 ppb in all tissues. Kidney contained the highest residues in cattle, while liver was higher in broilers. Milk residues from treated dairy cows averaged only 2.1 ppb. Extraction of liver and kidney using 50% KOH/ACN removed 23-68% of the total radioactive residues. Balance-excretion studies demonstrated that ≥98% of the administered radioactivity was eliminated in the feces of all species studied. Comparative metabolism studies demonstrated that ardacin was not significantly biotransformed as the parent compound was detected in excreta and tissues from cattle, broilers, and rats. Microbiological assays of tissue and fecal extracts confirmed the presence of ardacin as antimicrobial potency results paralleled those obtained by HPLC. The low tissue residues and favorable safety profile has qualified ardacin for 0-day withdrawal in both cattle and broilers.

Optimization of a Liquid Chromatographic Method for Determination of Malachite Green and Its Metabolites in Fish Tissues

A liquid chromatographic (LC) method was adapted and optimized for the determination of malachite green and its metabolites in fish plasma and muscle. Residues in plasma were extracted with acetonitrile, the extract was evaporated to dryness, and residues were resolubilized for LC analysis. Residues in muscle were extracted with an acetonitrile-acetate buffer mixture, reextracted with acetonitrile, and partitioned into methylene chloride with final cleanup on alumni and propylsulfonic acid solid-phase extraction columns. Residue levels were determined by using an LC cyano column with a PbO2 postcolumn and visible detection (618 nm). Overall mean recoveries of parent malachite green (MG-C) and its major metabolite, leuco-malachite green (MG-L), from plasma were 93 and 87%,respectively, at fortification levels ranging from 25 to 250 ppb. Overall mean recoveries of MG-C and MG-L from muscle were 85 and 95%, respectively, at fortification levels ranging from 5 to 100 ppb. Relative standard deviations (RSDs) of recoveries at all fortification levels ranged from 3.9 to 7.0% for plasma and from 2.1 to 5.2% for muscle. The method was applied to incurred residues in tissues sampled from catfish after waterborne exposure to [14C]MG-C. Mean recoveries of total radioactive residues in plasma and muscle throughout the extraction and cleanup process were 88 and 87%, respectively, and corresponding RSDs for MG-C and MG-L were in the same range as those for fortified tissues. MG-L was confirmed as the major metabolite of MG-C in catfish.

Metabolism of Imazethapyr (AC 263499) Herbicide in Corn

Imazethapyr [5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] is the active ingredient of imidazolinone PURSUIT herbicide. A confined plot field experiment was conducted to determine the metabolism of 14 C-6-pyridine-labeled imazethapyr in imidazolinone-tolerant corn after a single postemergence treatment at a rate of 0.25 lb ae/A, which is equivalent to 4 times the recommended use rate. The total radioactive residue in the corn plant was 15.35 ppm at 0 h after treatment and declined very rapidly to 0.28 ppm by 15 days. The residue in mature stalk/cob and seed at harvest was 0.08 and 0.02 ppm, respectively. The transport of radioactive residues to seed was minimal. Imazethapyr is metabolized very rapidly in corn

Metabolic fate of S,S,S-tributyl phosphorotrithioate (DEF) in the lactating goat.

1. Metabolism of [1-14C] DEF (S,S,S-1-14C-tributyl phosphorotrithioate, 1) in the lactating goat has been investigated. A goat was dosed orally by capsule on 3 consecutive days at a rate of 0.82 mg/kg body weight/day based on 25 times the maximum DEF residue anticipated in animal feed. 2. Urine and milk were collected throughout the study. The goat was killed 21 h following the last treatment, and kidney, liver and composite samples of muscle and fat were collected. The radioactive residue levels (following the three doses) were 3.45 ppm in liver, 0.35 ppm in kidney, 0.19 ppm in fat, 0.06 ppm in muscle and 0.12 ppm in milk collected at the final 16 h and prior to killing. 3. Urinary metabolic profile indicated that DEF was efficiently metabolized to many metabolites. Tissue and milk extracts also indicated that DEF was extensively metabolized. 4. DEF comprised 31 and 5% of the total radioactive residue in fat and milk, respectively. The amount of DEF in liver, kidney and muscle represented < 1% of the total radioactive residue. 5. A major metabolite, 3-hydroxybutylmethyl sulphone (HBM sulphone, UP3), was found in tissue, milk and urine. The identification of this metabolite was accomplished by a combination of MS, nmr and comparison with an authentic standard. The glucuronide (UP1) and sulphate (UP2) conjugates of HBM sulphone were found in urine, and the sulphate conjugate was a major metabolite in kidney. 6. The hydrolytic products of DEF, S,S-dibutyl phosphorodithioate (Dibufos, U16) and S-butyl phosphorothiate (Bufos, U8), were identified as minor components in urine, comprising 5 and 4% of the total radioactive residue, respectively. Butyl mercaptan was not found, but mixed disulphides of butyl mercaptan with either glutathione (U10, 3%) or N-acetyl cysteine (U13, 2%) were found. 7. Direct evidence for the incorporation of DEF residue into natural constituents was also established. Fatty acids from milk and fat were isolated and shown to be radioactive.

Bioconcentration of haloxyfop-methyl in bluegill ( Lepomis macrochirus rafinesque)

Bluegill ( Lepomis macrochirus Rafinesque) were exposed to a 14C haloxyfop-methyl [methyl 2-(4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy) propanoatel] concentration averaging 0.29 μg/L under flow-through conditions for 28 days. At the end of 28 days, the fish were transferred to clean water for a 4-day flow-through clearance period. Bluegill were found to rapidly absorb the ester from water which was then biotransformed at an extremely fast rate within the fish, such that essentially no haloxyfop-methyl was detected in the fish. The estimated bioconcentration factor for haloxyfop-methyl in whole fish was <17, based upon the detection limit for the ester in fish (0.005 μg/g) and the average concentration of haloxyfop-methyl in exposure water (0.29 μg/L). The principal component of the 14C residue within whole fish was haloxyfop acid [2-(4-((3-chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoic acid] which accounted for an average of about 60% of the total radioactivity. The high rate of biotransformation of the parent compound within the fish demonstrates the importance of basing the bioconcentration factor upon the actual concentration of parent material within the organism rather than the total radioactive residue levels for bioconcentration studies with radiolabeled compounds.

Drug residue formation from ronidazole, a 5-nitroimidazole. IV. The role of the microflora

When radioactive 1-methyl-5-nitroimidazole-2-methanol carbamate, ronidazole, labeled at the 4,5-ring positions was administered orally to germ-free and conventional rats, a much larger fraction of the radioactivity was excreted in the feces of the conventional animals. Determination of the total radioactive residues present in the carcass, blood, plasma, liver, fat and kidney 5 days after dosing indicated that the carcass of the germ-free animals contained a greater quantity of residue than that of conventional rats. On the other hand, the blood of the conventional animals contained a much higher level of radioactivity than that of the germ-free animals. These results show that while the microflora influence the distribution of the drug their presence is not obligating for the formation of persistent tissue residues in rats dosed with ronidazole.

Residues in Tissues and Eggs of Poultry Receiving Co-Ral (Bayer 21/199) in the Feed1

Radiophosphorus Co-Ral® ( O,O -diethyl O -(3-chloro-4-methylumbelliferone) phosphorothioate or Bayer 21/199) was mixed in laying mash at 100 p.p.m. and fed to laying hens for a maximum of 7 days. The highest concentration of total radioactive residues was in the liver and kidney; deposition of Co-Ral or metabolites in the fat was minor. The liver, kidney, and gizzard contained the highest concentration of acetonitrile-soluble materials. Acetonitrile-soluble residues were not present in any tissue after the hens were returned to normal feed for 7 days. Small hut detectable amounts of acetonitrile-soluble materials Were present in egg yolks analyzed at 11 to 15 days after treatment, but none was present in the albumin. about 79% of the radioactivity consumed in the feed was excreted in the feces by 28 days posttreatment; more than 85% of the excreted radioactive materials were hydrolytic products. Un-changed Co-Ral, the oxygen analog of Co-Ral ( O, O -diethyl phosphoric acid) and O, O -diethyl phosphorothioic acid were isolated and characterized from the feces.