Summary
Gangliosides may play functional roles in platelet physiology, therefore this study
has been designed to evaluate whether changes in ganglioside composition may occur
as a consequence of platelet activation. The results obtained indicate that lactosylceramide
and GM3 are the major glycosphingolipids of human platelets. The lipid-bound sialic
acid (LBS A) content was 1.27 ± 0.04µεg/mg of protein. Resting platelets 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 degranulation. Finally, incorporation of pyrene-labeled GM3 into platelet membranes,
followed by stimulation with adenosine diphosphate, resulted in the appearance of
a fluorescent band comigrating with GD3. The present studies indicate that sialyltransferase
activation may occur as an early event following platelet stimulation, leading to
GD3 synthesis mainly from the GM3 pool.
