[Interaction of platelets with monocytes with regard to arachidonic acid metabolites]

The aim of our study was the assessment whether internal peroxidase of arachidonic acid and/or prostaglandin can be transferred from platelets to monocytes. Monocytes were isolated from whole blood according to the method of Böyum. The monocytes cultures were led in the fluid environment, on the base of RPMI 1640 supplemented with autologous serum. Platelets were isolated from whole blood according to the method of Pinckard. During interaction of monocytes and platelets in the presence of indometacin we ascertained the increased of TXB2 concentrations in supper-natant. Incubation of monocytes in cultures stimulated by LPS in presence of indomethacin with platelets did not cause increased secretion of TXB2. Incubation of platelets with indomethacin in 36 h culture of monocytes stimulated by LPS caused increase concentration of 6-keto-PGF1alfa. The results of our study may suggest the presence of the one way transformation of the arachidonic acid from platelets to monocytes.

The role of monocytes in the platelet release of von Willebrand factor

Circulating blood monocytes, which are a source of foam cells contribute to the vascular lesions. Von Willebrand factor (vWF) is an adhesive multimeric glycoprotein that is synthesized only by endothelial cells and megakaryocytes. In the present study we assessed the ability of human platelets to secrete vWF after incubation with blood monocytes in vitro. Monocytes derived from blood of healthy adults were cultured and next incubated with washed platelets. von Willebrand factor antigen (vWF:Ag) was measured in the supernatant by Laurell immunoelectrophoresis. The study showed that Triton X-100 treated platelets released 82-112% of vWF:Ag. The levels of vWF:Ag in the supernatant with untreated platelets and incubated with monocytes without LPS were respectively 36-48% and 45-72%. After incubation washed platelets with LPS stimulated monocytes a significant decrease in vWF:Ag level was observed (7-11%).