GANGLIOSIDE CONTENT OF HUMAN PLATELETS - DIFFERENCES IN RESTING AND ACTIVATED PLATELETS

Gangliosides may play functional roles in platelet physiology. therefo re this study has been designed to evaluate whether changes in ganglio side composition may occur as a consequence of platelet activation. Th e results obtained indicate that lactosylceramide and GM3 are the majo r glycosphingolipids of human platelets. The lipid-bound sialic acid ( LBSA) content was 1.27 +/- 0.04 mu g/mg of protein. Resting plate lets did not express GD3; GD3 was synthesized upon platelet activation (24 +/- 8 ng/mg of protein). The stimulation of platelets with adenosine diphosphate showed the appearance of GD3 even in the absence of degran ulation. Finally, incorporation of pyrene-labeled GM3 into platelet me mbranes, followed by stimulation with adenosine diphosphate, resulted in the appearance of a fluorescent band comigrating with GD3. The pres ent studies indicate that sialyltransferase activation may occur as an early event following platelet stimulation, leading to GD3 synthesis mainly from the GM3 pool.