title: Potent platelet aggregation inhibitor from Trimeresurus gramineus snake venom.
abstract: Using DEAE-Sephadex A-50 column chromatography and gel filtration, a potent platelet aggregation inhibitor from Trimeresurus gramineus venom was purified. It was an acidic phospholipase A, rich in aspartic acid, glutamic acid and half-cystine, with an isoelectric point of 3.6. At a concentration of 10 micrograms/ml, the purified inhibitor showed a marked inhibitory effect on platelet aggregations induced by adenosine diphosphate, collagen, sodium arachidonate and ionophore A-23187 in rabbit platelet-rich plasma, washed platelet suspension, as well as in thrombin-degranulated platelet suspension. The ID50 of this venom inhibitor was about 2.5-5 micrograms/ml in platelet aggregations induced by all these aggregation inducers. The action of this inhibitor could be partially antagonized by phosphatidylethanolamine. High concentration of Ca2+ (5 mM) did not reverse the inhibitory action even in the presence of ionophore A-23187. The [14C]serotonin release induced by sodium arachidonate and thrombin was unaffected. Malonic dialdehyde formation induced by these aggregation inducers remained unchanged. Basal and prostaglandin E1-stimulated cAMP levels were not altered by this inhibitor. No lactate dehydrogenase was released even at a concentration of 62.5 micrograms/ml. Polylysine-induced platelet agglutination was not affected. beta-Mercaptoethanol inactivated both its phospholipase A enzymatic and platelet inhibitory activities, while p-bromophenacyl bromide only inactivated the former activity. The possibility of acting on a common final step of platelet aggregation, i.e. the intercellular adhesion between the activated platelets, was proposed.
mesh_terms: D000818:Animals; D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D003435:Crotalid Venoms / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D010740:Phospholipases / Q000302:isolation & purification*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D011817:Rabbits
chemical_list: D003435:Crotalid Venoms; D010740:Phospholipases; D010741:Phospholipases A