PLATELET SIALIC-ACID AND PLATELET SURVIVAL AFTER AGGREGATION BY ADP

  • 1 January 1980
    • journal article
    • research article
    • Vol. 56  (5) , 876-880
Abstract
Some investigators have reported recently that platelet surface sialic acid is decreased during ADP-induced aggregation, whereas others have reported an increase. Since removal of sialic acid from the platelet surface shortens platelet survival, the survival of platelets that have been aggregated by ADP was determined. The amount of sialic acid in the suspending fluid of platelets after ADP-induced aggregation was also measured. ADP-induced aggregation did not cause the loss of sialic acid from rabbit platelets (which do not undergo a release reaction in response to ADP) nor from washed human platelets in a medium containing physiologic concentrations of Ca in which granule contents are not released. In a medium without added Ca, ADP caused the release of 14C-serotonin (42.5% .+-. 3%) from human platelets, but < 4% of the sialic acid-containing material was released. Little of the releasable sialic acid of platelets is in the dense granules or the .alpha.-granules. Thrombin (5 U/ml) released 90.0% .+-. 3.4% of the serotonin from human platelets but only 20.6% .+-. 7.4% of the total sialic acid-containing material. Neuraminidase removed 42.3% of the total sialic acid, presumably from the platelet surface. Rabbit platelets that had been aggregated by ADP and deaggregated survived normally when returned to the circulation. The platelets apparently did not lose membrane sialic acid during aggregation and deaggregation.