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°C. These effects should be taken into consideration when
TMB-8 is used as a calcium antagonist in platelets.
Key words
TMB-8 - Calcium antagonists - Platelet leakage - Serotonin loss - Platelet inhibitor