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Fibronectin modulates the activation of human platelets
F Sinigaglia1, M Torti, G Ramaschi
1Department of Biochemistry, Faculty of Sciences, University of Pavia, Italy.
Biochemical and Biophysical Research Communications
|December 29, 1989
Summary
Plasma fibronectin inhibits mild activation of human platelets. It reduces calcium movement and protein phosphorylation, suggesting a role in regulating platelet responses.
Area of Science:
- Biochemistry
- Hematology
- Cellular Biology
Background:
- Platelet activation is crucial for hemostasis and thrombosis.
- Fibronectin is a plasma protein involved in cell adhesion and wound healing.
- Understanding modulators of platelet responsiveness is key to managing thrombotic disorders.
Purpose of the Study:
- To investigate the effect of plasma fibronectin on human platelet activation.
- To determine fibronectin's influence on platelet responses to low-dose agonists like thrombin and ADP.
- To elucidate potential mechanisms underlying fibronectin's modulatory effects.
Main Methods:
- Measurement of cytoplasmic calcium levels in activated platelets.
- Assessment of cyclic AMP (cAMP) levels following agonist stimulation.
- Analysis of protein phosphorylation in thrombin-activated platelets.
Main Results:
- Plasma fibronectin significantly reduced cytoplasmic calcium movement in platelets activated by low doses of thrombin or ADP.
- Fibronectin attenuated the decrease in cAMP levels induced by low-dose thrombin but not ADP.
- A dramatic decrease in protein phosphorylation was observed in platelets treated with low-dose thrombin and fibronectin.
Conclusions:
- Plasma fibronectin acts as an inhibitor of mild human platelet activation.
- Fibronectin's inhibitory effect on thrombin-activated platelets may involve the glycoprotein IIb-IIIa complex.
- A distinct, yet unidentified, mechanism likely mediates fibronectin's effect on ADP-activated platelets.