Fibronectin modulates the activation of human platelets.
In this paper we studied the effect of plasma fibronectin on platelet responsiveness to low doses of thrombin or ADP. Fibronectin causes: (i) a significant lowered cytoplasmic calcium movement in platelets activated both with low doses of thrombin and with ADP, (ii) a lowered decrease of the cAMP level induced by low thrombin, but not by ADP, (iii) a dramatic decrease of protein phosphorylation in low thrombin-treated platelets. The results reported here demonstrate that plasma fibronectin behaves like an inhibitor of mild activations of human platelets; its effect is probably mediated by the glycoprotein llb-llla complex in thrombin activated platelets, whereas a different and unknown mechanism must be supposed to explain the results obtained with ADP-activated platelets.
Sinigaglia
F
F
Department of Biochemistry, Faculty of Sciences, University of Pavia, Italy.
Torti
M
M
Ramaschi
G
G
Balduini
C
C
D000244:Adenosine Diphosphate / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000097:blood; D000242:Cyclic AMP / Q000097:blood; D003593:Cytoplasm / Q000378:metabolism; D005353:Fibronectins / Q000494:pharmacology*; D006801:Humans; D010750:Phosphoproteins / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects*; D010980:Platelet Membrane Glycoproteins / Q000502:physiology; D013917:Thrombin / Q000494:pharmacology
D005353:Fibronectins; D010750:Phosphoproteins; D010980:Platelet Membrane Glycoproteins; D000244:Adenosine Diphosphate; D000242:Cyclic AMP; D013917:Thrombin; D002118:Calcium