Related Experiment Video
Updated: Jun 7, 2026
09:38
A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time
Published on: February 14, 2017
Polyphosphoinositide Changes in Rabbit Platelets Stimulated with Platelet Activating Factor During the Formation of
J D Vickers1, R L Kinlough-Rathbone, M A Packham
1Department of Pathology, Faculty of Health Sciences, McMaster University, Hamilton, Canada.
Platelets
|November 4, 2010
Summary
Platelet activating factor (PAF) stimulates phosphoinositide metabolism, particularly phosphatidylinositol 4,5-bisphosphate (PIP2) degradation to PIP, during fibrin clot formation. This process requires both fibrin polymerization and platelet secretion for full effect.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Phosphoinositide metabolism plays a crucial role in platelet activation and function.
- Platelet activating factor (PAF) is a potent stimulator of platelet responses.
- Fibrin formation is a key event in hemostasis and thrombosis, involving platelet aggregation.
Purpose of the Study:
- To investigate the impact of polymerizing fibrin on platelet phosphoinositide metabolism stimulated by PAF.
- To elucidate the roles of fibrin network formation and platelet granule secretion in PAF-induced phosphoinositide changes.
- To determine if PAF-stimulated phospholipase C activity is further enhanced during clot formation.
Main Methods:
- Rabbit platelets were prelabeled with radioactive phosphate and inositol.
- Platelet phosphoinositide metabolism was stimulated by PAF in the presence of polymerizing fibrin or fibrinogen.
- Lipid extracts were analyzed to quantify changes in phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 4-phosphate (PIP).
- The effect of blocking fibrin polymerization (using GPRP) and thromboxane A2 formation was assessed.
Main Results:
- Stimulation with PAF in the presence of polymerizing fibrin led to a greater decrease in PIP2 compared to fibrinogen alone.
- This PIP2 decrease was largely accounted for by an increase in PIP formation, suggesting PIP2 hydrolysis.
- Fibrin polymerization and platelet secretion were both necessary for the association of inositol phosphates with interfacial proteins.
- PAF-stimulated phospholipase C activity was not further increased by clot formation.
Conclusions:
- Polymerizing fibrin significantly enhances the degradation of PIP2 to PIP in PAF-stimulated platelets.
- Both fibrin network formation and platelet granule secretion are essential for specific interfacial protein labeling.
- The study clarifies the complex interplay between fibrin, platelet activation, and phosphoinositide signaling during clot formation.
More Related Videos
Related Concept Videos
01:42Phosphoinositides and PIPs
Phosphoinositides are a group of phospholipids containing a glycerol backbone with two fatty acid chains and a phosphate attached to a myoinositol sugar ring. The inositol head group extends into the cytoplasm, where it is modified by adding phosphate groups to form phosphatidylinositol phosphates or PIPs.
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
01:22Formation of the Platelet Plug
The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
01:18Structure and Function of Platelets
The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 μm and a thickness of roughly 1 μm. They play a crucial role in the body's vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000 platelets, with...
01:16Clot Retraction and Fibrinolysis
After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.
01:11IP3/DAG Signaling Pathway
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
01:17Intracellular Signaling Affects Focal Adhesions
Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Some...