Release of β lysin from platelets by thrombin and by a factor produced in heparinized blood

Abstract

Removal of calcium by either citrate, oxalate, or ethylenediamine tetraacetate inhibited coagulation of blood at an early stage and prevented the release of β-lysin from platelets. In contrast, heparin caused platelet agglutination and stimulated β-lysin release in vitro and in vivo. This release was calcium dependent and may have been due to a calcium dependent reaction in the blood coagulation sequence. Thrombin which bypassed the early calcium dependent stages of coagulation directly stimulated the release of β-lysin from platelets. However, thrombin alone or in combination with other plasma factors was not as effective in releasing β-lysin as the regular coagulation process. Thrombin's platelet degranulating activity correlated with its β-lysin releasing activity. In contrast to thrombin, staphylococcal coagulase, which also bypassed the calcium dependent stages of coagulation, coagulated citrated blood without releasing β-lysin. The release of β-lysin was observed previously in the absence of blood coagulation, but this is the first observation of coagulation without β-lysin release. It is clear that β-lysin is released from platelets during coagulation by the direct action of thrombin and that it may be released in an earlier calcium dependent reaction.