RECONSTITUTED HIGH-DENSITY-LIPOPROTEIN (RHDL) MODULATES PLATELET ACTIVITY IN-VITRO AND EX-VIVO

A reconstituted high density lipoprotein (rHDL) prepared for clinical use was tested for its influence on platelet activity modulated by var ious stimuli. In a first series of in vitro experiments, rHDL was adde d to blood in a concentration series, and platelet rich plasma (PRP) w as isolated. Platelets were stimulated with arachidonic acid, collagen , epinephrine or ADP, and platelet aggregation was assessed. rHDL medi ated a dose dependent inhibition of the platelet activity. With purifi ed platelets rHDL inhibited the release reaction induced by collagen, but not by thrombin, as measured by CD62P (P-Selectin) expression on t he plasma membrane. Ex vivo experiments were performed with PRP from v olunteers, previously infused with 25 mg rHDL/kg body weight and 40 mg rHDL/kg body weight, respectively. Platelet activity in PRP was asses sed before. and up to 30 h after the end of the rHDL infusion. A trans ient inhibition of the platelet aggregation induced by arachidonic aci d and collagen was observed which was more pronounced in the group rec eiving 40 mg rHDL/kg body weight. In both groups of experiments, in vi tro and ex vivo, the inhibition of the platelet activity was also depe ndent on the stimulus used.