| Abstract: | While platelet derived growth factor (PDGF) did not induce any platelet aggregation nor secretion, it modified the polyphosphoinositide metabolism of human platelets prelabeled with 32P-orthophosphate. We found a decrease of 32P associated with phosphatidylinositol 4,5 bisphosphate after 3 min, with parallel increase of 32P-phosphatidylinositol 4 phosphate and 32P-phosphatidylinositol using 100 ng/ml of PDGF. This modification was PDGF concentration dependent. PDGF inhibited thrombin and collagen induced platelet aggregation and 14C-serotonin release in a dose dependent manner, but was without effect when arachidonic acid was used. These results suggest that PDGF (i) stimulated the hydrolysis of polyphosphoinositides (ii) and could exert a negative feedback control on platelet activation induced by thrombin or collagen. |
