The role of calcium in the equilibrium between assembled and disassembled microtubules was investigated in human platelets. The two pools of microtubule protein was "frozen" by addition of a glycerol-dimethyl sulfoxide-containing medium and were estimated by measuring the colchicine binding activities of total and polymerized tubulin. Addition of A23187 to platelet rich plasma produced a transient decrease in the pool of polymerized tubulin within 30 sec., followed by a return to base-line values within 2 min.. Total content of platelet tubulin remained unchanged during the course of aggregation. TMB-8, a known intracellular calcium antagonist, abolished this transient decrease in polymerized tubulin induced by A23187, while indomethacin did not. These findings strongly suggest the important role of intracellular calcium in microtubule assembly-disassembly.
ASJC Scopus subject areas