Cytoskeletal F-actin assembly and microtubule reorganization are principal cellular events responsible for activation-induced platelet shape change; however, their roles in regulating platelet secretion have remained controversial. Herein, label-free microelectrochemistry techniques and pharmacological approaches are used to probe the role of F-actin and the microtubule in platelet dense-body secretion. Altered microtubule integrity via exposure to paclitaxel or vincristine had no effect on serotonin release in platelet suspensions. Disruption of F-actin by cytochalasin D (CytoD) or latrunculin A (LatA) substantially enhanced the rate of serotonin release, while inhibition of the F-actin-dependent platelet motor protein myosin IIA by blebbistatin had no effect. CytoD-treated platelets also showed enhanced serotonin quantal secretion rate. These results clearly indicate that F-actin, but not the microtubule, regulates platelet dense-body secretion and does so by serving as a physical barrier. This study also demonstrates the promise of microelectrochemistry for giving important insight into platelet quantal secretion mechanisms in future studies.
Bibliographical noteFunding Information:
The authors gratefully thank D. Freeman for rabbit blood draws and M. Krumwiede for her help with TEM studies. This study is generously supported by the National Institute of Health New Innovator Award under the grant no. 1 DP2 OD004258-01 and Camille Dreyfus Teacher-Scholar Award to C.L.H.