Species Difference in Developmental Toxicity of an N‐Phenylimide Herbicide between Rats and Rabbits and Sensitive Period of the Toxicity to Rat Embryos

Abstract

Abstract An N‐phenylimide herbicide, S‐53482, exhibited developmental toxicity in rats in the absence of maternal toxicity at a dose of 30 mg/kg. The developmental toxicities noted were embryolethality, teratogenicity (mainly ventricular septal defect [VSD] and wavy ribs) and growth retardation. In contrast to rats, the herbicide showed no developmental toxicity in rabbits even at a maternal toxic dose of 3,000 mg/kg. There was a remarkable species difference between rats and rabbits. A single dose of S‐53482 was administered to pregnant rats on one of gestation days 11 through 15 (detection of plug = day 0). Day 12 of gestation was the most sensitive day for embryonic death, VSD, and decreased fetal body weight. It is likely that there is a common mechanism for the three types of developmental toxicity and that S‐53482 does not produce VSD by its direct damage to embryonic heart tissue.