Apolipoprotein B release from activated human platelets.

Area of Science:

• Biochemistry
• Hematology
• Immunology

Background:

• Platelets play a crucial role in hemostasis and thrombosis.
• Apolipoprotein B (apoB) is a major component of low-density lipoproteins (LDL).
• The presence and release of apoB from platelets are not well understood.

Purpose of the Study:

• To investigate the release of apolipoprotein B (apoB) from activated human platelets.
• To characterize the conditions and mechanisms of apoB release.

Main Methods:

• Washed human platelets were activated using various agonists (thrombin, Ca2+-ionophore A23187, U46619).
• Apolipoprotein B (apoB) release was quantified using enzyme-linked immunosorbent assay (ELISA).
• Density gradient ultracentrifugation was employed to determine the density of released apoB.

Main Results:

• Platelet activation with thrombin, A23187, or U46619 stimulated the release of approximately 20 ng apoB/10(8) platelets.
• Thrombin-induced apoB release was inhibited by the prostacyclin analogue carbacyclin.
• The dose-response curves for apoB and beta-thromboglobulin (beta-TG) release were similar, as was the inhibition by carbacyclin.
• Density gradient ultracentrifugation showed that released apoB was primarily in the LDL density range.
• Heparin treatment did not affect apoB levels or thrombin-induced release.

Conclusions:

• Human platelets contain immunoreactive apolipoprotein B (apoB).
• Platelet activation triggers the release of apoB, suggesting its involvement in platelet function.
• The release mechanism shares similarities with that of beta-thromboglobulin (beta-TG).