Elsevier

Placenta

Volume 18, Issue 7, September 1997, Pages 547-552
Placenta

Original article
Uptake of microparticles by rat visceral yolk sac

https://doi.org/10.1016/0143-4004(77)90009-1Get rights and content

Abstract

The visceral yolk sac (VYS) is responsible for a major part of the amino acid nutrition of the early post-implantation rat embryo and possibly also at the fetal stage of gestation. The mechanism involves endocytic uptake of proteins by the tissue's epithelial cells followed by intralysosomal digestion to amino acids. The amino acids so generated are used for protein synthesis in both the embryo and the VYS. Previous reports had indicated that the endocytic capacity of the VYS might be limited to exclude larger macromolecules. This study demonstrates that Percoll, which comprises 30-nm silica particles coated with polyvinylpyrrolidone (PVP), is as effectively captured by the 17.5-day rat VYS cultured in vitro as PVP itself. Uptake of 125I-labelled Percoll was progressive with time over 5 h and was inhibited by a low incubation temperature, 2,4-dinitrophenol (50 μg/ml), EGTA (5 mM), colchicine (10 μg/ml) or cytochalasin B (10 μg/ml). After uptake of 125I-labelled Percoll, VYSs released only 20 per cent of their radioactivity when re-incubated in fresh medium for 3 h. These data, and electron micrographs showing Percoll in intracellular vacuoles, are all consistent with uptake by endocytosis. Percoll's rate of uptake by the VYS indicates that, like 125I-labelled PVP, it enters the cell chiefly by fluid-phase pinocytosis. It is concluded that endocytosis by the VYS will efficiently capture even the largest globular proteins, and that previous indications of a relatively low size exclusion reflected the loosely coiled configuration of the synthetic polymers used in the earlier studies.

Reference (28)

  • PrattenM.K. et al.

    Pinocytosis and phagocytosis: the effect of size of a particulate substrate on its mode of capture by rat peritoneal macrophages cultured in vitro

    Biochimica et Biophysica Acta

    (1986)
  • YoungD. et al.

    Uptake and processing of59Fe-labelled and125I-labelled rat transferrin by early organogenesis rat conceptuses in vitro

    Placenta

    (1997)
  • DuncanR. et al.

    Effect of molecular size of 1251-labelled poly(vinylpyrrolidone) on its pinocytosis by rat visceral yolk sacs and rat peritoneal macrophages

    Biochemical Journal

    (1981)
  • FreemanS.J. et al.

    Evidence that protein ingested by the rat visceral yolk sac yields amino acids for synthesis of embryonic protein

    Journal of Embryology and Experimental Morphology

    (1983)
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    a

    Present address: Department of Human Anatomy and Cell Biology, University of Nottingham, Queen's Medical Center, Nottingham, NG7 2UH, UK.

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