Electron microscopy of lanthanum in plasma

Area of Science:

• Biomedical research
• Electron microscopy
• Vascular biology

Background:

• Lanthanum nitrate is an electron microscopic tracer for studying vascular permeability.
• The particle size of lanthanum nitrate tracers in vivo is not well-defined.

Purpose of the Study:

• To determine the size and distribution of lanthanum nitrate tracer particles in the blood circulation of rabbits.

Main Methods:

• Intravenous injection of lanthanum nitrate into living rabbits.
• Electron microscopic examination of plasma and blood components.
• Analysis of tracer localization in plasma, blood cells, and fibrin clots.

Main Results:

• Electron-dense lanthanum tracer particles were observed in rabbit plasma 30 minutes post-injection.
• The tracer was found associated with blood cells and concentrated in fibrin clots.
• Lanthanum was absent in serum, indicating binding to components removed during clotting.

Conclusions:

• Ionic lanthanum injected into circulation largely binds to fibrinogen.
• The smallest tracer particle size corresponds to the fibrinogen molecule (m.w. 330,000).
• Larger lanthanum-containing particles are also present in the circulation.