| Abstract: | Platelet aggregation as well as [14C] serotonin release were increased in platelet-rich plasma in comparison to gel-filtered platelet preparation. The addition of red blood cells to platelet-rich plasma enhanced thrombin-induced [14C] serotonin release by 7%, whereas in a gel-filtered platelet preparation free of any plasma constituents a 47% increment was noted. In the presence of white blood cells, no effect could be shown. Purified lipoproteins were incubated (in their normal plasma concentration) with gel-filtered platelets for 30 minutes at 37 degrees C, and the effect on in vitro platelet function was studied. Very low density lipoprotein and low density lipoprotein increased thrombin-induced platelet aggregation and [14C] serotonin release induced by epinephrine, ADP, and thrombin. In contrast, high density lipoprotein inhibited these platelet functions. Lipoprotein-deficient plasma increased platelet aggregation and release reaction. It appears that plasma lipoproteins have a profound effect on in vitro platelet function. Since both platelets and lipoproteins are of importance in atherosclerosis, the platelet-lipoprotein interaction might be of major significance in this process. |
