Increased resorption of embryos in O,O,S-trimethyl phosphorothioate-treated rats.

Pregnant rats (N = 7) were dosed p.o. with O,O,S-trimethyl phosphorothioate (OOS-TMP) (LD50 = 85) at 20 mg/kg on days G8 and G10. Seven animals were treated with corn oil and pair-fed. Five control animals were treated with corn oil. The abdomen was palpated on day G15 and in 4 animals out of 7 treated with OOS-TMP, complete resorption was observed. All pair-fed and control animals maintained pregnancy until day G21. Total number of resorption/number of implants was 60/95 (63.2%) in OOS-TMP animals, 21/82 (25.6%) in pair-fed animals and 4/65 (6.5%) in control animals. Incidence of complete resorption and % resorption were significantly higher (P less than 0.03 and P less than 0.01) in comparison with those in pair-fed animals. Fetuses from OOS-TMP mothers showed slight growth retardation. By skeletal examination, a missing vertebra and delayed ossifications were found in animals treated with OOS-TMP (20 mg/kg).