title: A novel pattern of placental leucine transfer during mid to late gestation in a highly placentotrophic viviparous lizard.
abstract: Placentotrophy is the nourishment of embryos by resources provided via the placenta during gestation. The magnitude and timing of placental nutrient support during pregnancy are important for embryonic growth, especially in highly placentotrophic animals such as mammals. However, no study has yet investigated how placental organic nutrient support may change during pregnancy in highly placentotrophic viviparous reptiles. Amino acids are essential nutrients for embryonic growth and leucine is a common amino acid. The magnitude and timing of placental leucine transfer may affect embryonic growth and mass and, therefore, offspring phenotype. In this study, female Pseudemoia entrecasteauxii, a highly placentotrophic viviparous skink, were collected throughout gestation. We injected (3)H-leucine into these gravid females and assessed the transfer of (3)H-leucine into maternal compartments (i.e., the blood and the liver), and into embryonic compartments (i.e., the embryo, the yolk, and the amniotic fluid). At either 60 or 120 min post-injection, the radioactivity in each sample was extracted and then counted, and the transfer ratio was calculated. Our results provide direct evidence that circulating maternal leucine passes through the placenta into the embryos in this species. The relative rate of placental leucine transfer did not alter during mid to late gestation. This suggests the steady somatic growth of the embryos during mid-late pregnancy is dependent upon the placental transfer of nutrients rather than yolk stores. This pattern of placental nutrient support may determine offspring body size at birth and, therefore, offspring fitness in P. entrecasteauxii.
authors: School of Zoology, University of Tasmania, Hobart, Tasmania, Australia.
authors: Keisuke
authors: K
authors: Itonaga
authors: Erik
authors: E
authors: Wapstra
authors: Susan M
authors: SM
authors: Jones
mesh_terms: D000704:Analysis of Variance; D000824:Animal Nutritional Physiological Phenomena / Q000502:physiology*; D000818:Animals; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D005260:Female; D007930:Leucine / Q000378:metabolism / Q000493:pharmacokinetics*; D008116:Lizards / Q000196:embryology*; D008322:Mammals / Q000196:embryology; D011247:Pregnancy; D012588:Scintillation Counting; D013648:Tasmania; D013997:Time Factors; D014316:Tritium / Q000493:pharmacokinetics; D052286:Viviparity, Nonmammalian / Q000502:physiology*
chemical_list: D014316:Tritium; D007930:Leucine