Iron accumulation by bovine aortic endothelial cells

Area of Science:

• Cell Biology
• Biochemistry
• Physiology

Background:

• Understanding iron transport mechanisms in endothelial cells is crucial for cellular iron homeostasis.
• Transferrin is the primary iron carrier in circulation, necessitating study of its interaction with endothelial cells.

Purpose of the Study:

• To investigate the mechanisms of iron and transferrin binding and transport in bovine aortic endothelial cells.
• To elucidate the role of transferrin receptors and other factors in cellular iron uptake.

Main Methods:

• Utilized diferric bovine transferrin labeled with 59Fe to study iron uptake.
• Employed enzymatic and chemical treatments (trypsin, ammonium chloride, methylamine) and calcium to assess transport pathways.
• Investigated energy dependence using electron transport inhibitors and confirmed transferrin receptors via isolation, SDS-PAGE, and autoradiography.

Main Results:

• Demonstrated saturable, receptor-mediated iron uptake from transferrin, sensitive to trypsin, ammonium chloride, and methylamine, with calcium reversing effects.
• Identified approximately 1.5 x 10^6 transferrin receptors per cell with a Kd of 9.1 x 10^-7 M.
• Observed non-endocytic iron uptake of ferrous iron, unaffected by receptor-mediated endocytosis inhibitors, and enhanced by calcium.

Conclusions:

• Bovine endothelial cells transport iron through two distinct mechanisms: receptor-mediated endocytosis of transferrin-bound iron and a non-endocytic pathway for ferrous iron.
• Calcium plays a significant role in modulating iron uptake, potentially promoting the non-endocytic mechanism.
• The presence of a ferrireductase suggests a role in facilitating non-transferrin-bound iron uptake.