Transmission of radioactivity into eggs from laying hens (Gallus domesticus) administered tritium labeled T-2 toxin

Revisión: Implicaciones toxicológicas y nutricionales de la toxina T-2 / Review: Toxicological and nutritional implications of T-2 toxin

Trichothecenes are mycotoxins produced by species of the genus Fusarium. These toxins are associated with health problems in humans and animals. The most common trichothecenes in cereals are deoxynivalenol, HT-2 toxin, diacetoxyscirpenol, nivalenol, neosolaniol and T-2 toxin; the latter is the most widely studied because it is easy to produce in the laboratory. The effects of T-2 toxicosis include dermatonecrosis, reduced body weight and efficiency of food utilization, severe diarrhoea, haemorrhage, necrosis of the upper alimentary tract, anaemia, immuno suppression ; and in birds, poor feathering. This paper reviews the latest information about the occurrence, chemical characteristics, toxicity, metabolic alterations, biotransformation and detoxifi cation methods of the T-2 toxin.

Fusariotoxins in Avian Species: Toxicokinetics, Metabolism and Persistence in Tissues

Fusariotoxins are mycotoxins produced by different species of the genus Fusarium whose occurrence and toxicity vary considerably. Despite the fact avian species are highly exposed to fusariotoxins, the avian species are considered as resistant to their toxic effects, partly because of low absorption and rapid elimination, thereby reducing the risk of persistence of residues in tissues destined for human consumption. This review focuses on the main fusariotoxins deoxynivalenol, T-2 and HT-2 toxins, zearalenone and fumonisin B1 and B2. The key parameters used in the toxicokinetic studies are presented along with the factors responsible for their variations. Then, each toxin is analyzed separately. Results of studies conducted with radiolabelled toxins are compared with the more recent data obtained with HPLC/MS-MS detection. The metabolic pathways of deoxynivalenol, T-2 toxin, and zearalenone are described, with attention paid to the differences among the avian species. Although no metabolite of fumonisins has been reported in avian species, some differences in toxicokinetics have been observed. All the data reviewed suggest that the toxicokinetics of fusariotoxins in avian species differs from those in mammals, and that variations among the avian species themselves should be assessed.

Chicken cytochrome P450 1A5 is the key enzyme for metabolizing T-2 toxin to 3'OH-T-2

The transmission of T-2 toxin and its metabolites into the edible tissues of poultry has potential effects on human health. We report that T-2 toxin significantly induces CYP1A4 and CYP1A5 expression in chicken embryonic hepatocyte cells. The enzyme activity assays of CYP1A4 and CYP1A5 heterologously expressed in HeLa cells indicate that only CYP1A5 metabolizes T-2 to 3'OH-T-2 by the 3'-hydroxylation of isovaleryl groups. In vitro enzyme assays of recombinant CYP1A5 expressed in DH5α further confirm that CYP1A5 can convert T-2 into TC-1 (3'OH-T-2). Therefore, CYP1A5 is critical for the metabolism of trichothecene mycotoxin in chickens.

Measurement of T-2 and HT-2 toxins in eggs by high-performance liquid chromatography with fluorescence detection

T-2 toxin is a mycotoxin produced by several species of common fungi capable of infesting human food and animal feeds. Lower-quality feeds given to chickens may be contaminated with T-2 toxin, which may affect their health. The literature suggests that T-2 toxin is transmitted from the hen to the eggs. This article describes the development of a liquid chromatographic assay for T-2 and the related mycotoxin HT-2 in eggs. T-2 and HT-2 toxins were isolated from spiked eggs with a tandem charcoal-alumina-Florisil column and immunoaffinity column cleanup. The isolated toxins were derivatized with the fluorophore 1-anthroyl nitrile, separated by high-performance liquid chromatography, and quantitated by fluorescence. The limit of detection of the method was 1 ng ml(-1) (parts per billion) of T-2 and HT-2 in whole (with shell removed) eggs. The limit of quantitation for both toxins was 5 ng ml(-1). Recoveries from spiked eggs over the range from 5 to 50 ng ml(-1) averaged 89.2% for T-2 and 100.3% for HT-2, with coefficients of variation of 3.5 and 8.2%, respectively. This method is sensitive enough to be used to check for the presence of T-2 or HT-2 toxins in eggs.

Elimination of oxolinic acid in eggs after oral treatment of laying hens

1. Oxolinic acid is often used in poultry as a therapeutic agent. The aim of this study was to determine both its elimination into eggs, following oral dosing through the drinking water (12 mg/kg/d) or diet (13 mg/kg/d) for 5 d and its plasma concentrations. 2. Samples (albumen, yolk, plasma) were analysed by high performance liquid chromatography (HPLC) with fluorimetric detection. The limits of quantification were 10 ng/g in plasma and 5 ng/g in albumen and yolk. Residues were much higher in albumen than in plasma, whereas they were lower in yolk. 3. 95% of the overall oxolinic acid detected in eggs was concentrated in the albumen. 4. Detectable residues persisted for 9 d and 7 d, respectively, in albumen and yolk after the treatment was discontinued.

Transmission of residues to eggs following long-term administration of 14C-labelled deoxynivalenol to laying hens

The transmission of radioactive residues of 14C-labelled deoxynivalenol (DON; vomitoxin) to eggs was investigated during prolonged administration of low levels of DON-contaminated feed to White Leghorn chickens. Laying hens were provided with a 5.5 ppm 14C-DON-spiked diet (.55 mg DON; .8.25 microCi bird/day) for a 65-day period, after which they received a clean, unadulterated diet for 21 days. Total residues (based on specific radioactivity) increased daily until the 8th day of 14C-DON exposure, when levels reached a plateau for several days, then decreased slowly thereafter. Maximum radioactivity measured was equivalent to 1.7 micrograms DON or metabolites per 60-g egg; the yolk, albumen, and shell membrane contributed 70, 29, and 1% of the total amount, respectively. By Day 30, levels had declined to 25% of peak levels (.40-micrograms DON equivalents/egg) and remained relatively constant until the spiked feed was removed at Day 65, at which time residues quickly declined to negligible values. These findings indicate that although very low concentrations of DON can be found in eggs under these feeding conditions, levels are so low that a potential health hazard to humans would likely be minimal.