Abstract
Metabolic fate of a ureid herbicide, 1-(α, α-dimethybenzyl)-3-(p-tolyl) urea, dimuron, was investigated in male rats. Greater than 69% of orally administered carbonyl-14C-dimuron (50mg/kg, single) was absorbed from the gastrointestinal tract of male Wistar rats. Furthermore, the dose was entirely eliminated in the feces (66%) and urine (34%) within 48hr after dosing. Tissue retention accounted for only 0.6% of the dose within 48hr after administration. Radiocarbon levels in selected tissues declined to less than detectable levels (liver: 0.2ppm, kidney: 0.03ppm, adipose tissue: 0.15ppm, blood: 0.025ppm, plasma: 0.02ppm, carcass: 0.05ppm equivalent of dimuron) after 120hr. The high elimination observed in the feces was mainly due to active biliary excretion (38.6% in 48hr). A substantial part (24.3%) of the radioactive biliary excreta was reexcreted into the bile through an enterohepatic cycle. In addition to urinary and biliary excretion, the involvement of the gastrointestinal tract was observed as a minor excretion route of dimuron. Tlc of the urine extracts indicated that dimuron was metabolized to more than seven polar metabolites, but dimuron itself was not detected in the urine. From fecal extracts, dimuron and several of its metabolites were detected. A major metabolite found in the urine was suggested as 1-(α, α-dimethylbenzyl)-3-(p-carboxyphenyl) urea by Tlc. As minor metabolites, p-toluidine was detected in the urine, and the expiration of radioactive carbon dioxide was also observed (less than 0.06% of the dose). Furthermore, radioactive β-glucuronide conjugate was detected in the bile.
