Subcellular localization of 111In in human and rabbit platelets

Area of Science:

• Biomedical Science
• Cell Biology
• Hematology

Background:

• Platelets play crucial roles in hemostasis and thrombosis.
• Understanding platelet labeling and radiotracer distribution is vital for diagnostic imaging and research.
• Subcellular localization of radiolabeled compounds influences their biological behavior and potential applications.

Purpose of the Study:

• To investigate the subcellular distribution of 111In-oxine in human and rabbit platelets.
• To explore the uptake mechanisms and release dynamics of radiolabeled platelets.
• To compare platelet labeling characteristics between human and rabbit models.

Main Methods:

• Electron microscopy (EM) autoradiography with a hypothetical grain technique was used for subcellular analysis.
• Platelets were labeled with 111In-oxine in plasma-free and plasma-containing systems.
• Inhibitors of 5-hydroxytryptamine (5-HT) uptake were employed to assess active transport.
• Stimulation with collagen and thrombin was used to evaluate radiolabel release.

Main Results:

• 111In in rabbit platelets concentrated in dense bodies, especially in plasma-free labeling.
• Human platelets accumulated 111In primarily in the cytosol.
• No active uptake process for 111In-oxine was demonstrated in either species using tested inhibitors.
• Collagen and thrombin induced dose-dependent release of radioactivity from rabbit platelets, mimicking 5-HT release and inhibited by indomethacin.

Conclusions:

• Subcellular localization of 111In-oxine differs significantly between human and rabbit platelets.
• Rabbit platelet dense bodies are key sites for 111In accumulation.
• Platelet activation by collagen and thrombin can release accumulated 111In from rabbit platelets.
• The findings suggest distinct mechanisms of radiotracer handling in different species' platelets.