Influence of granulocyte elastase-like proteinase (ELP) on platelet functions.

The influence of granulocyte elastase-like proteinase (ELP) on platelet functions was investigated. ELP inhibited the platelet aggregations induced by a wide variety of agonists. The inhibition was marked in the case of receptor-mediated agonists such as thrombin, ristocetin, etc. It was moderate with the pervading agonist, arachidonic acid, and mild with the bypassing agonist, Ca2+ ionophore A23187. ELP inhibited the release of thromboxane A2 from platelets in the case of the platelet aggregation induced by thrombin. On the other hand, ELP did not inhibit the release of thromboxane A2 from platelets in the platelet aggregation induced by arachidonic acid or Ca2+ ionophore A23187. ELP suppressed the release of serotonin from platelets induced by thrombin, while it did not markedly suppress the release of serotonin induced by Ca2+ ionophore A23187. Treatment of platelets with ELP resulted in a slight increase of intraplatelet cAMP levels. These results suggest that ELP acts on receptors and inhibits platelet functions. As a results, ELP markedly inhibits the platelet functions such as aggregation or release of serotonin or thromboxane A2 stimulated by receptor-mediated agonists. ELP slightly elevates the cAMP level in the platelets, resulting in the mild inhibition of the platelet functions stimulated by the pervading agonist, arachidonic acid, or the bypassing agonist, Ca2+ ionophore A23187.