Urinary and biliary metabolic patterns of chlorothalonil in germ-free and conventional rats

The metabolic fate of chlorothalonil, a broad spectrum fungicide that is kn own to be metabolized via glutathione conjugation, was examined through the analysis of urine and bile metabolites. The role of digestive microflora i n the metabolism of chlorothalonil was assessed by comparing the metabolic patterns in germ-free and conventional rats. Low urinary and biliary excret ion of radioactivity was observed in both conventional and germ-free rats. However, the urinary excretion of radioactivity was higher in conventional than in germ-free rats. Radio-HPLC analysis of urine and bile showed a comp lex metabolic profile in both conventional and germ-free rats. Methylthio m etabolites of chlorothalonil were determined in ethyl acetate extracts of u rine and bile of conventional and germ-free rats. These metabolites were ex creted in a higher amount in the urine of conventional rats than in the uri ne of germ-free rats. This study shows the complexity of chlorothalonil met abolism and the role of the digestive microflora in chlorothalonil metaboli sm.