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Chick hepatic lectins: an electron microscopic study on isolated hepatocytes during development
L Falasca1, P Mattioli, L Dini
1Department of Biology, University of Rome Tor Vergata, Italy.
Insights
Hepatocytes exhibit distinct carbohydrate recognition patterns during development. N-acetylglucosamine (GlcNAc) and mannose receptors are present in embryonic and neonatal chicks, while N-acetylgalactosamine (GalNAc) receptors are specific to early embryonic stages.
Area of Science:
- Cell Biology
- Developmental Biology
- Glycobiology
Background:
- Hepatocytes play a crucial role in carbohydrate metabolism and recognition.
- Understanding the developmental changes in cell surface receptors is vital for comprehending liver function.
- Carbohydrate-binding proteins (lectins) mediate crucial cellular interactions.
Purpose of the Study:
- To investigate the ontogeny of carbohydrate recognition systems in developing hepatocytes.
- To localize and quantify specific lectin binding sites on hepatocytes during embryogenesis and early post-hatching life.
Main Methods:
- Isolation of hepatocytes from chick embryos at 16 and 19 days of development, and from newly hatched chicks.
- Ultrastructural localization and quantification of binding sites using protein-gold complexes.
- Analysis of binding sites for terminal N-acetylglucosamine (GlcNAc), mannose, and N-acetylgalactosamine (GalNAc) residues.
Main Results:
- Hepatocytes from all studied stages (embryonic and neonatal) display binding sites for GlcNAc and mannose residues.
- GalNAc-specific binding sites are exclusively detected on hepatocytes from 16-day-old embryos.
- The number and distribution of these lectin binding sites vary significantly with developmental stage.
Conclusions:
- A significant modulation of GlcNAc and mannose specific receptors occurs on the hepatocyte cell surface between embryonic development and neonatal life.
- The transient presence of GalNAc receptors in early embryonic hepatocytes suggests a specific role during early development.
- These findings highlight the dynamic nature of hepatocyte carbohydrate-binding receptors during avian development.
Abstract:
We studied the carbohydrate recognition systems of hepatocytes isolated from 16-day-old embryos, 19-day-old embryos and chicks within 24 h of hatching. We localized and quantified at the ultrastructural level the binding sites for glycoproteins exposing terminal N-acetylglucosamine (GlcNAc), mannose and N-acetylgalactosamine (GalNAc) residues by means of protein-gold complexes. Binding sites specific for GlcNAc and mannose residues are present on hepatocytes from embryos and chicks. On the contrary GalNAc specific binding sites are exclusively observed on cells from 16-day-old embryos. The number and distribution of gold particles on hepatocyte cell surfaces depend on the binding sites and the age considered. We describe a modulation in the number of GlcNAc, and mannose specific receptors present on the cell surface between the embryonal stage and neonatal life.