Mechanism of Developmental Effects in Rats Caused by an N-Phenylimide Herbicide: Transient Fetal Anemia and Sequelae during Mid-to-Late Gestation.

Background: Rat developmental toxicity including embryolethality and teratogenicity (mainly ventricular septal defects [VSDs] and wavy ribs) was produced by an N-phenylimide herbicide that inhibits protoporphyrinogen oxidase (PPO) common to chlorophyll and heme biosynthesis. Major characteristics of the developmental toxicity included species difference between rats and rabbits, compound-specific difference among structurally similar herbicides, and sensitive period. Protoporphyrin accumulation in treated fetuses closely correlated with the major characteristics.

Dermal developmental toxicity of N-phenylimide herbicides in rats.

Background: S-53482 and S-23121 are N-phenylimide herbicides and produced embryolethality, teratogenicity (mainly ventricular septal defects and wavy ribs), and growth retardation in rats in conventional oral developmental toxicity studies. Our objective in this study was to investigate whether the compounds induce developmental toxicity via the dermal route, which is more relevant to occupational exposure, hence better addressing human health risks.

Methods: S-53482 was administered dermally to rats at 30, 100, and 300 mg/kg during organogenesis, and S-23121 was administered at 200, 400, and 800 mg/kg (the maximum applicable dose level).