HUMAN UMBILICAL VEIN ENDOTHELIAL-CELLS - SPECIFIC BINDING OF PLATELET-ACTIVATING-FACTOR AND CYTOSOLIC CALCIUM FLUX

An interaction of the platelet-activating factor (Paf) with endothelial cells was investigated using human umbilical vein endothelial cells. Confluent endothelid cells bound [H-3]Paf in the presence of 0.25% fatty acid-free serum albumin after culture in media containing either heat-inactivated foetal calf serum or serum substitute. The Scatchard analysis of the saturated specific [H-3]Paf binding showed a B-max of 2.5 fmol indicating 2800 binding sites per endothelial cell. [H-3]Paf binding was partially reversible at 200 and 40 and endothelial cells partially metabolized [H-3]Paf at 200 but not at 40. [H-3]Paf binding and Paf-mediated increase of cytosolic free calcium were inhibited by specific Paf receptor antagonists which do not interfere with Paf metabolism Immortalized umbilical vein endothelial cells bound [H-3]Paf specifically after culture in the presence of insulin (20 hr, 0.4 U/mL) with non-specific binding in the absence of insulin. The results show that specific Paf binding mediated calcium flux in human endothelial cells.