Parallel inhibition of spontaneous and antigen-induced platelet histamine release

¹ Department of Pharmacology, The University of Texas Southwestern Medical School, Dallas, Texas

Small amounts of histamine and serotonin are released spontaneously in vitro from blood cells of normal rabbits. Similar to release induced by antigen-antibody reaction, spontaneous release is calcium dependent but occurs even in the presence of a high concentration of heparin. Spontaneous release is inhibited by tosylarginine and tosylarginine methyl ester, agents which also inhibit antigen-induced release. Benzoylarginine, benzoylarginine methyl ester, lysine ethyl ester, and arginine have little effect on either spontaneous or antigen-induced release. A heat-stable factor in plasma can effect platelet amine release. The results suggest that factors involved early in the coagulation mechanism may be responsible for platelet amine release under these conditions.