Placental morphology of rats prenatally exposed to methyl parathion.

Although prenatal exposure to pesticides has been associated with numerous adverse reproductive effects, data on the effects of such toxics in the placenta is limited. Thus, the present study was carried out to determine the morphology of the rat placenta exposed to the organophosphate pesticide methyl parathion (MP) in ad libitum fed and restricted diet animals. The pregnant females were randomly divided into control groups and experimental groups, the latter of which received MP at the doses of 0.0, 1.0, 1.5 and 2.0 mg/kg. Most cells in the maternal-fetal interface showed significant alterations in the presence of MP. Trophoblast giant cells exhibited either prominent characteristics of degeneration or normal morphology with many phagosome vacuoles, apparently containing cell debris. Vascular congestion was also more frequent in the labyrinth of the treated animals. Areas of fibrosis and hemorrhage were found in the decidua, as well as decidual cells presenting pyknotic nuclei and acidophilic cytoplasm. In the placentas of females treated with both restricted diet and MP, such changes were much more severe. Together, these alterations suggest a direct, toxic effect of MP on the placental cells. The phagocytic activity exhibited by trophoblast cells, may be playing a role in the removal of death cells from the maternal-placental interface and/or in a compensatory mechanism to maintain the uptake of maternal nutrients, following decreased metabolic exchange functions of the labyrinth due to the toxic effect of the MP.