Conditions influencing platelet lysis.

When platelets take part in the formation of hemostatic plugs and thrombi in vivo, electron microscopic evidence indicates that some of the platelets not only release their granule contents but also undergo lysis. In the present study we have examined, in vitro, the relation between the release reaction of platelets and platelet lysis in response to the release-inducing agents thrombin and collagen. Release was measured by determining the amounts of 14C-serotonin and adenine nucleotides that appeared in the ambient fluid of prelabeled platelets. Lysis was measured by determining the amount of either lactate dehydrogenase or 14C-labeled cytoplasmic ATP from platelets incubated with -14C-adenosine. Washed platelets prepared from rabbit, pig, or human blood lost some lactate dehydrogenase and 14C-ATP upon exposure to thrombin, but the amounts of lactate dehydrogenase and 14C-ATP lost from rabbit platelets were much greater than from pig or human platelets. The reason for this species difference is not aparent. The platelet release reaction appeared to be necessary for lysis to occur. Reduction of the extent of the release reaction by preincubation of rabbit platelets with metabolic inhibitors to deplete metabolic ATP reduced the extent of lysis. In addition, it was apparent that the fall in platelet metabolic pool ATP caused by thrombin was not responsible for platelet lysis. Lack of calcium, addition of prostaglandin E(1), OR Increasing the albumin concentration of the suspending medium of rabbit platelets inhibited platelet lysis. These conditions may prevent the loss of material that causes lysis, inhibit the action of this lost material, or inhibit the lytic reaction. Release and lysis may occur together and release can occur without detectable lysis, but lysis in response to a release-inducing agent does not take place unless the release reaction occurs.