Effects of 8-(N, N-diethylamino)ocytl 3, 4, 5-trimethoxybenzoate HCl (TMB-8) on washed blood platelets with special reference to a specific loss of serotonin.

8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate HCl (TMB-8) has been used to indicate involvement of Ca++ in platelet activities, but possible other effects have not been investigated. This study investigates TMB-8-induced leakage of cytoplasmic content and specific loss of one granule constituent, serotonin from washed platelets. TMB-8 concentrations above 0.5 mM block secretion initially and induce leakage after short time incubation. TMB-8 (0.15 mM) enhances a slow release of serotonin, but inhibits a slow release of low affinity platelet factor 4 antigen which take place when washed platelets are incubated at pH 7.4 and 37 degree C. These effects should be taken into consideration when TMB-8 is used as a calcium antagonist in platelets.