Metabolism of propachlor by the germfree rat.

Three major metabolites of propachlor were isolated from the excreta of germfree rats given 14C-labeled propachlor orally. In contrast, 11 urinary metabolites, six of which were 2-methylsulfonylacetanilides not present in excreta of germfree rats, were isolated from control rats given 14C-labeled propachlor orally. Enterohepatic circulation and microbial metabolism in the intestine were necessary for production of the methylsulfonyl-containing and other metabolites of propachlor in the conventional rat.