Determination of flumequine in channel catfish by liquid chromatography with fluorescence detection.

Rapid methods are described for determination of flumequine (FLU) residues in muscle and plasma of farm-raised channel catfish (Ictalurus punctatus). FLU residues were extracted from tissues with an acidified methanol solution, and extracts were cleaned up on C18 solid-phase extraction cartridges. FLU concentrations were determined by liquid chromatography (LC) using a C18 analytical column and fluorescence detection (excitation, 325 nm; emission, 360 nm). Mean recoveries of FLU from fortified muscle were 87-94% at 5 levels ranging from 10 to 160 ppb (5 replicates per level). FLU recoveries from fortified plasma were 92-97% at 5 levels ranging from 20 to 320 ppb. Limits of detection (signal-to-noise ratio, 3:1) for the method as described were 3 and 6 ppb for muscle and plasma, respectively. Relative standard deviations (RSDs) for recoveries were < or = 12%. Live catfish were dosed with 14C-labeled or unlabeled FLU to generate incurred residues. Recoveries of 14C residues throughout extraction and cleanup were 90 and 94% for muscle and plasma, respectively. RSDs for incurred FLU at 2 levels in muscle and plasma ranged from 2 to 6%. The identity of FLU in incurred tissues was confirmed by LC/mass spectrometry.

Pharmacokinetics, tissue distribution and metabolism of acriflavine and proflavine in the channel catfish (Ictalurus punctatus).

1. The disposition of proflavine (PRO) and acriflavine (ACR) were examined in channel catfish after intravascular (i.v.) dosing (1 mg/kg) or waterborne exposure (10 mg/l for 4 h). 2. After i.v. dosing, plasma concentration-time profiles of parent PRO and ACR were best described by two- and three-compartment pharmacokinetic models respectively. Terminal elimination half-lives of PRO and ACR in plasma were 8.7 and 11.4 h respectively. 3. In animals dosed with 14C-PRO or 14C-ACR, total drug equivalent concentrations were highest in the excretory organs and lowest in muscle, fat and plasma. In PRO-dosed animals, residues in the liver and trunk kidney were composed primarily of glucuronosyl and acetyl conjugates of PRO; residues in muscle were composed mostly (> 95%) of the parent drug. In ACR-dosed animals, the parent compound comprised > 90% of the total residues in all tissues examined. 4. PRO and ACR were poorly absorbed in catfish during waterborne exposure. At the end of a 4-h exposure, parent PRO and ACR concentrations in muscle were 0.064 and 0.020 microgram/g respectively. Levels in muscle declined below the limit of determination (0.005 microgram/g) within 1-2 weeks.

Liquid chromatographic determination of acriflavine and proflavine residues in channel catfish muscle.

A liquid chromatographic (LC) method was developed for determination of acriflavine (ACR) and proflavine (PRO) residues in channel catfish muscle. Residues were extracted with acidified methanol solution, and extracts were cleaned up with C18 solid-phase extraction columns. Residue concentrations were determined on an LC cyano column, with spectrophotometric detection at 454 nm. Catfish muscle was individually fortified with ACR (purified from commercial product) and PRO at concentrations of 5, 10, 20, 40, and 80 ppb (5 replicates per level). Mean recoveries from fortified muscle at each level ranged from 86 to 95%, with relative standard deviations (RSDs) of 2.5 to 5.7%. The method was applied to incurred residues of ACR and PRO in muscle after waterborne exposure of channel catfish to commercial acriflavine (10 ppm total dye for 4 h). RSDs for incurred residues of ACR and PRO were in the same range as those for fortified muscle. Low residue concentrations (< 1% of exposure water concentration) suggested poor absorption of ACR and PRO in catfish.

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.

Furazolidone disposition after intravascular and oral dosing in the channel catfish.

1. The pharmacokinetics, tissue distribution and excretion of the nitrofuran drug furazolidone have been examined in the channel catfish. [14C]Furazolidone was administered by intravascular or oral routes in a single dosage of 1 mg/kg body weight. 2. A two-compartment pharmacokinetic model best described parent furazolidone concentrations in the plasma after intravascular dosing. Elimination of parent compound was extremely rapid, with a terminal half-life of 0.27h and total body clearance of 1901 ml/h/kg. 3. After oral dosing, furazolidone concentrations in the plasma were highest at 1 h and were below the limit of determination (< 20 ng/ml) at 5 h. The oral bioavailability of parent furazolidone administered in solution was 58%, compared with 28% in a feed mixture. 4. Concentrations of furazolidone and its metabolites were highest in the excretory tissues and lowest in the muscle after oral dosing. Parent furazolidone comprised 10% of the total 14C in the muscle at 8 h and was not detectable (< 1 ng/g) at 24 h; total 14C concentrations declined from 274 to 59 ng furazolidone equiv./g between 8 and 168 h. Non-extractable (bound) residues comprised 18% of total 14C in muscle at 8 h and 33% at 168h. 5. Renal excretion was the primary route of elimination of 14C residues and accounted for nearly 55% of the oral dose.

Comparison of maturation of drug-metabolizing enzymes in calves with functioning or nonfunctioning rumen.

Drug-metabolizing enzyme activities were measured in livers from calves fed commercial milk replacer (nonfunctioning rumen [veal]), and those fed milk replacer supplemented with whole grain and hay from the first week of age (functioning rumen [ruminating calves]). After birth, cytochrome P450 and its NADPH-dependent reductase activities remained unchanged in veal calves; in ruminating calves they increased almost 50%. Cytochrome P450-mediated reactions, such as aniline hydroxylase activity, tripled in ruminating calves, but remained unchanged in veal calves. In both groups of calves, coumarin hydroxylase and 7-ethoxycoumarin 0-deethylase activities increased after birth, but maturation rates and activity values in ruminating calves were considerably greater than those of veal calves. The aminopyrine N-demethylase activity for veal calves was equal to that of calves with functioning rumen. Uridine diphosphoglucuronic acid glucuronyl transferase and glutathione-S-transferase activities also were higher in calves with functioning rumen than in veal calves. This increased activity in calves with functioning rumen probably represents a response to environmental exposure to xenobiotics. Compared with rumen-functional calves, bob veal (0 to 3 weeks old) and fancy veal (15 to 19 weeks old) calves fed commercial milk replacer have a significantly (P = 0.05) diminished capacity for metabolizing drugs and other xenobiotics. From a regulatory perspective, the variance in drug-metabolizing enzyme activities within these different market classes of calves suggests that specific studies designed to determine drug residue-depletion times in veal calves may be needed.

Liquid chromatographic determination of furazolidone in shrimp.

A liquid chromatographic (LC) method was developed for the quantitation of furazolidone residues in shrimp muscle. The shrimp homogenate (1.0 g) is extracted with acetonitrile, and the extract is taken to dryness. The residue is dissolved in acetonitrile, and the solution is passed through alumina and C18 cleanup columns. The eluate is taken to dryness and reconstituted in a suitable solvent for reversed-phase (C18) LC with UV detection at 365 nm. Recoveries of furazolidone from shrimp homogenates spiked from 5 to 80 ng/g ranged from 74.3 to 79.7%, and relative standard deviations (RSDs) were 5.0-8.9%. RSDs for incurred furazolidone quantitated at 5.9 and 9.2 ng/g were 6.6 and 7.6%, respectively.

Maturational development of drug-metabolizing enzymes in sheep.

A qualitative and quantitative assessment was made of the development of hepatic drug-metabolizing enzymes (DME) in sheep as part of a study of the ability of the food-producing species to metabolize drugs. The following DME and components were measured in this study: cytochromes P-450 and b5 and NADPH and NADPH-dependent reductases associated with each of these cytochromes; cytochrome P-450-mediated reactions, including aniline and coumarin hydroxylases, aminopyrine N-demethylase, and 7-ethoxycoumarin 0-deethylase; a uridine diphosphoglucuronic acid glucuronyl transferase with 4-methylumbelliferone as substrate; and glutathione-S-transferase with dinitrochlorobenzene and dichloronitrobenzene as substrates. Amounts or activities of most of these components and enzymes increased up to and beyond the time of weaning. Amount of cytochrome b5 and uridine diphosphoglucuronic acid transferase activity were not affected by age, whereas NADPH cytochrome c (P-450) reductase activity actually decreased after weaning. In some instances (eg, coumarin hydroxylase, cytochrome P-450, and dinitrochlorobenzene-glutathione-S-transferase), differences from preweaning DME values were observed only after sheep were greater than or equal to 6 months old. All other DME activities were definitely increased, compared with the values in lambs before weaning (0 to 12 weeks old). Approximately a third of the sheep studied had some type of clinical disease that might have affected the DME activities. Diseases were classified as sore mouth, pneumonia, foot rot, parasitism, and systemic bacterial infections. Except in a few instances, these diseases had minimal effect on DME activities measured in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Maturational development of drug-metabolizing enzymes in dogs.

A qualitative and quantitative assessment was made of the development of hepatic drug-metabolizing enzymes (DME) in dogs as part of a study of the ability of animal test species to metabolize drugs. The following DME variables were measured in this study: amount of cytochromes P-450 and b5; activity of the NADPH and NADH-dependent reductases associated with each of these cytochromes; activity of cytochrome P-450-mediated enzymes, including aniline and coumarin hydroxylases, aminopyrine N-demethylase, and 7-ethoxycoumarin O-deethylase; activity of a uridine diphosphoglucuronic acid glucuronyl transferase with 4-methylumbelliferone as substrate; and glutathione-S-transferase activities, with dinitrochlorobenzene and dichloronitrobenzene as substrates. Most enzyme components had achieved maximal amount or activity by the fifth to eighth week after birth; they tended to decrease after weaning, although the activity of dichloronitrobenzene-glutathione transferase in geriatric dogs (312 to 525 weeks old) was approximately twofold greater than that of 8-week-old pups. There were no gender-related differences in any of the enzyme amounts or activities determined. Individual variation was pronounced even in the homogeneous colony from which these dogs were obtained.