[Significance of gastrointestinal microflora for the metabolism of foreign compounds]

In vitro transformation of the Fusarium mycotoxins deoxynivalenol and zearalenone by the normal gut microflora of pigs

The biotransformation of the Fusarium mycotoxins deoxynivalenol and zearalenone by the normal bacterial gut flora of pigs was examined in this in vitro study. For that purpose, suspensions of intestinal contents (duodenum, jejunum, caecum, colon, rectum) of porcine origin were incubated anaerobically with deoxynivalenol (DON) or zearalenone (ZEA). DON and ZEA were degraded by the flora of the caudal segments (caecum, colon, rectum) of the gut--particularly the colon content--whereas the microorganisms of the cranial segments (duodenum, jejunum) exhibited no transforming activity. DON was showed to be deepoxidated, ZEA was hydrolyzed to alpha-zearalenol and an unknown metabolite. The transformation of DON was correlated with a loss of cytotoxicity, which could be demonstrated in the MTT(3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium++ + bromide)-cell-culture assay using swine kidney cells as target cells. The results of the study presented here correspond with the data found in in vivo studies. On the basis of these findings one could conclude that this in vitro method seems to be well suited to the study of the transformation of mycotoxins by the microflora of the gut. The in vitro study is cheaper than a feeding trial, and the preliminary information on the metabolism of mycotoxins obtained in such studies is helpful in designing feeding trials more clearly. Besides the simple and fast handling, reproducibility and the protection of the animals studied are further advantages of this in vitro method. In connection with the MTT-cell-culture assay, additional information about the cytotoxic potential of the bacterial transformation products can be obtained.

[The effect of azoxybenzene on microsomal liver enzymes in the rat]

Oral administrations of azoxybenzene (0, 25, 50 and 100 mg/kg b.w.) over a period up to 7 days caused a time and dose dependent decrease in the amount of cytochrome P-450 as well as in the ability of aminopyrine-N-demethylation and aniline hydroxylation in the hepatic microsomes of male and female rats. In both sexes there were retardations in the body weight gain and increases in the relative weight of the liver. The amount of the microsomal cytochrome b5 was increased.