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DOI: 10.1080/019262302753559614 Pregnancy Dating in the Rat: Placental Morphology and Maternal Blood ParametersOrganon, Department of Toxicology and Drug Disposition, P.O. Box 20, 5340 BH Oss, The Netherlands, eveline.derijk{at}organon.com
Organon, Department of Toxicology and Drug Disposition, P.O. Box 20, 5340 BH Oss, The Netherlands
University of Nijmegen, Department of Animal Physiology, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands The rat is commonly used as a model in studies on embryology and reproduction toxicology. Surprisingly, the current literature does not provide a comprehensive reference data set on placental development in rat. Therefore, we have evaluated morphological changes of the placenta and maternal blood parameters during pregnancy of the Sprague—Dawley rat. The morphologic data presented in this study may be useful as reference material. This study revealed that placental development in the rat is a well-defi ned process, characterized by key synchronized morphological events at specifi c points in time, convenient for laboratory practice and provides the toxicologist with a sensitive tool to distinguish between normal and abnormal placental development and to detect fetal and placental mismatches. During rat pregnancy, signifi cant changes were observed in maternal blood parameters strongly reminiscent of those observed in pregnant women. These changes included: (a) decreased blood cell volume as a result of hemodilution, (b) increased white blood cell counts refl ecting the response of the mother to the fetal allograft, (c) increased blood clotting values, (d) decreased plasma glucose and increased lipid content maximizing fetal glucose availability and maternal energy conservation, and (e) decreased electrolyte values refl ecting plasma volume expansion. It was concluded that the combined data set on placental morphology and maternal blood parameters in pregnant rats provides powerful tools for recognition of abnormal pregnancies.
Key Words: Rat pregnancy dating placenta histopathology hematology clinical chemistry.
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