Hepatic porphyria induced by the herbicide tralkoxydim in small mammals is species‐specific

Abstract Tralkoxydim is the active ingredient in a postemergent herbicide used in cereal crops. During preregistration trials, tralkoxydim was observed to cause hepatic porphyria and cholestasis in laboratory mice. Porphyria was not seen in similarly exposed rats or hamsters, but data were not collected regarding the susceptibility of any wild small mammal species to the tralkoxydim‐induced porphyria. To address this data gap, we exposed small mammals to tralkoxydim, to 3,5‐diethoxycarbonyl‐1,4‐dihydrocol‐lidine (DDC; a known porphyrinogenic chemical), or to sunflower oil alone. We studied small mammal species that might be exposed following agricultural applications of the herbicide, including the white‐footed mouse ( Peromyscus leucopus ), the deer mouse ( P. maniculatus ), and the meadow vole ( Microtus pennsylvanicus ). Because of their known susceptibility to both tralkoxydim‐and DDC‐induced porphyria, commercially supplied Mus musculus (CD‐1 Swiss mice) were exposed as positive‐control animals. We also exposed offspring of wild‐caught M. musculus to compare their responses to those of the commercially supplied animals. Potential hepatotoxicity was determined by assessing the accumulation of liver protoporphyrin. Of the species tested, only M. musculus was susceptible to the porphyrinogenic action of tralkoxydim, and no significant accumulation of protoporphyrin was observed in any of the other species exposed to the herbicide.