Metabolism of propyrisulfuron: 14C excretion, 14C concentration in plasma and tissues, and amount of metabolites in rats

1. Metabolism of a novel sulfonylurea herbicide, propyrisulfuron [1-(2-chloro-6-propylimidazo[1,2-b]pyridazin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea] labeled at the C-1 position of the propyl group and C-5 position of the pyrimidine ring with C-14 was investigated after a single oral administration in male and female rats. 2. Administered C-14 was excreted into the urine (5.7-29.8%) and feces (64.6-97.4%), respectively. C-14 concentration in plasma reached a maximum level at 4 to 12 h post-administration and then decreased rapidly with a biological half-life of approximately 23 to 32 h. Total C-14 residues in the whole body were <0.1-1.4%, suggesting that the residues were not accumulated in the tissues. 3. The amount of metabolites in urine, feces, and bile were quantified using high-performance liquid chromatography (HPLC). There were no differences in metabolites found between male and female rats. 4. The absorption for the low dose (5 mg/kg) and the high dose (1000 mg/kg) was estimated to be approximately 90% and 20%, respectively, suggesting a saturable absorption. 5. The plasma protein binding in male and female rats was >= 98.8%, suggesting that propyrisulfuron had a strong affinity to plasma proteins.