Metabolite identification cattle

Metabolism studies showed that the major metabolites of the components of ivermectin in cattle, sheep, and rats were 24-hydroxymethyl compounds, whereas major metabolites in swine were 3-0-desmethyl compounds. Identification of the 24-hydroxymethyl metabolites has not been yet achieved in swine, whereas identification of Hie 3-O-desmetlryl metabolites has not been made possible in cattle or sheep (54, 55). Recent metabolism studies (56) in cattle, swine, and rats have indicated, however, diat the metabolism of avermectins was qualitatively similar for all three species. There were quantitative differences both between species and between compounds for a given species, but all three species produced... 

In cattle feces, 64% of the total residues was identified as diethylstilbestrol, 23% as 3-(p-hydroxyphenyl)-2-hexene-4-one, and less than 1% as 4 -hydroxypro-piophenone (43). The identification of 4 -hydroxypropiophenone as a metabolite of diethylstilbestrol implies that dienestrol is formed through an epoxide-diol pathway and that these metabolites show electrophilic reactivity (45). These observations have to be seen in connection with the mutagenic and carcinogenic activity of diethylstilbestrol and possibly also the other stilbene estrogens. 

Profiling and identification of flunixin and its metabolites in the liver and kidneys of male and female feeder cattle was also carried out during the second total residue depletion study. Initially, liver tissue from cattle treated intravenously with... 

Table II summarizes the results of the previous and recent metabolism studies with IVM and AVM. The identifications of the major ( ) and minor ( ) in vivo (liver) and in vitro (liver microsome) metabolites determined for cattle, rat and swine in these recent studies are included with the data from Table I. The metabolism of IVM and AVM is qualitatively similar for all three species and in vivo and in vitro metabolism is similar for each species. There are quantitative differences between species (compare the metabolism of IVM by rat and cattle with that by swine) and between compounds for a given species (compare the metabolism of IVM and AVM by rat), but all three species produce either 24-OHMe- or 3"-ODMe-metabolites as the major metabolite and the other compound as a minor metabolite. The rat is therefore an appropriate laboratory animal toxicity model for both cattle and swine for IVM and AVM.

Srinivas and Srinivasulu (1993) found that heulandate layers developed with carbon disulfide-pyridine (1 1) were effective for the separation of steroid hormones,—dehydroepiandrosterone could easily be separated from mixtures of cholesterol and estradiol benzoate or testosterone phenylpropionate, and testosterone could be separated from mixtures of cholesterol and testosterone phenylpropionate or estradiol benzoate. Likewise, estradiol could easily be separated from mixtures of cholesterol and estradiol benzoate. Daeseleire et al. (1994) applied HPTLC and GC/MS for the detection of anabolic steroids used as growth promoters in illicit cattle fattening within the European market. Agrawal et al. (1995) developed a sensitive, reliable, and rapid silica gel TLC method for the separation, identification, and quantification of stereospecific androgen metabolites. 

Advantages of MS MS are the decreased background noise due to the isolation of the parent ion and the subsequent fragmentation. In this way, similar fragments not originating from interferences (sample constituents or column bleed) with a mass comparable to the parent ion cannot be present and will not interfere with the analysis [40]. Recent (unpublished) work in our laboratory demonstrated the power of GC-MS-MS (ion trap) as an important tool for the identification of chloroandrostenedione (CLAD), a metabolite of chlorotestoster-one, at a level of 0.2 pg/L in urine samples of cattle. 

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