THE DAMI CELL POSSESSES THE PLATELET COLLAGEN RECEPTOR VLA-2, BUT DOES NOT MOBILIZE CALCIUM

Flow cytometric and Western blot analysis showed that Dami cells posse ss the major platelet collagen adhesion receptor, the integrin VLA-2, and that VLA-2 was expressed in higher levels in a time-dependent mann er in DMSO-induced Dami cells. Both control and DMSO-induced Dami cell s were able to adhere to collagen as measured in a microtiter-based ad hesion assay. It appeared that collagen adhesion was solely mediated b y VLA-2, since inclusion of a monoclonal antibody directed against the alpha-2 subunit of VLA-2 in the adhesion assay was able to totally in hibit adhesion. Although Dami cells possess a variety of platelet mark ers, and are able to mobilize intracellular calcium in response to ADP , U-46619, and thrombin, they were unable to respond to collagen chall enge. We concluded that Dami cells may lack some key transducing eleme nt present in platelets that prevents them from being activated by col lagen.