A comparison of the distribution, metabolism and excretion of ethylenethiourea in the pregnant mouse and rat

Pregnant mice and rats were treated by stomach intubation on day 15 g of gestation with 240 mg/kg of ethylenethiourea (ETU) made up in part with radiolabeled ETU. Animals were sacrificed at specific times post-treatment, and maternal tissues, fetus, urine and feces were collected for determination of radioactivity. Maternal and fetal tissue levels of ETU were similar at three hours post treatment; thereafter, the mouse (maternal and fetus) showed much less ETU than the rat. The t1/2 of ETU elimination from the maternal blood was 9.4 and 5.5 hours for the rat and mouse, respectively. Analysis of urine by thin-layer chromatography and radiochromatography revealed that the mouse and rat metabolized ETU by different pathways. Furthermore, the mouse is able to metabolize ETU to a greater extent than the rat.