Cycasin Excretion in Conventional and Germfree Rats

Summary

Urinary and fecal excretion of the naturally occurring toxic and carcinogenic glycoside, cycasin, β-D-glycosyloxyazoxymethane, was determined in germfree and conventional Sprague-Dawley male rats. Excretion in germfree rats was nearly quantitative while only 18 to 35% was recovered in conventional rats. Since cycasin is inert until acted upon by a β-glucosidase, the lack of enzymatic cleavage in germfree rats suggests the bacterial flora as the most likely source for the enzyme in conventional rats. Considerable variation was encountered in the amount of cycasin which was not recovered and was presumably metabolized in conventional rats. The possible significance of this variability is discussed in relation to toxicity and carcinogenicity.