Evaluation of the teratogenic effects of Tri-ortho-cresyl phosphate in the Long-Evans hooded rat.

The developmental toxicity of tri-ortho-cresyl phosphate (TOCP) was evaluated in Long-Evans rats. Pregnant rats were treated with 87.5, 175, and 350 mg/kg/day TOCP throughout organogenesis from gestation Days 6 through 18 (Day of sperm = Day 0). The highest dose tested (350 mg/kg) was lethal in 28% of the dams; no maternal deaths or toxicity were observed in the 87.5 or 175 mg/kg dose groups. There were no significant differences noted among the experimental and control groups for preimplantation loss or resorption. Fetal weights for both sexes in the TOCP groups were significantly greater than in the control group; however, no difference among the TOCP groups was observed. Malformation rates were too low to warrant statistical analysis. Numerous soft tissue and skeletal variations were observed in both control and TOCP-treated groups; there were no significant differences in the frequency of variations among the dose groups. The results of this study indicate that TOCP is not teratogenic in the Long-Evans rat.