Ultrastructural study of endothelial permeability to macromolecules in fetal paraplacental capillaries of European badger.
Permeability of the continuous placental capillaries to macromolecules has been studied in the hemophagous region of the badger placenta by perfusion in situ of cationized ferritin (CF) in three phases of gestation (days 10 to 22, 22 to 30, and 30 to 40 after ovo-implantation). This ultrastructural tracer mapped luminal microdomains; such fixation on the luminal cell membrane was a preliminary step before its internalization into the cytoplasm. Lateral intercellular spaces (LIS) and vesicles were found to play an evolving role during gestation. Ultrastructural maturation of the capillary may be related to evolution of endothelial permeability. The LIS are involved in the transport of this macromolecule during the first two-thirds of pregnancy, and become progressively impermeable to the tracer as true, tight junctions are established between the adjacent endothelial cells. The enlargement of the vesicular population in luminal, cytoplasmic and abluminal positions and the increase in microfilaments could make vesicular transport more efficient in favouring cellular contractility. These ultrastructural findings that indicate that the optimal endothelial permeability to CF occurs during the second phase of pregnancy when the paraplacental hematoma reaches its maximal development and functional activity.
Dumartin
B
B
Laboratoire d'Histologie-Embryologie, Universitié de Bordeaux II (U.F.R. II), Bordeaux, France.
Canivenc
R
R
D000818:Animals; D002199:Capillary Permeability; D004848:Epithelium / Q000648:ultrastructure; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D005293:Ferritins / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008322:Mammals; D008431:Maternal-Fetal Exchange; D008854:Microscopy, Electron; D010920:Placenta / Q000098:blood supply*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*
D005293:Ferritins