The mechanism of enhanced parathion/paraoxon toxicity during pregnancy was examined. Enhanced toxicity following exposure to paraoxon in the pregnant mouse as determined by cholinesterase suppression was observed at 0.10 and 0.58 mg/kg after ip administration on Day 19 of gestation. However, there were no significant differences in cholinesterase activity between pregnant animals and virgin controls after either po or iv paraoxon. Higher systemic and lower hepatic levels of parathion were demonstrated in pregnant mice following ip administration of parathion (5 mg/kg). Data herein also suggest that during pregnancy, larger quantities of paraoxon bypass initial liver detoxification after ip dosing. The mechanism of increased toxicity of parathion/paraoxon during pregnancy may result from alterations in absorption from the peritoneal cavity.
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