MORPHOMETRY OF PLATELET INTERNAL CONTRACTION

  • 1 January 1984
    • journal article
    • research article
    • Vol. 115  (3) , 412-417
Abstract
Blood platelets [human] have a characteristic discoid shape supported by a circumferential band of microtubules. Following stimulation by aggregating agents or foreign surfaces, platelets lose their discoid form, extend pseudopods and undergo a process of internal reorganization. Randomly dispersed cytoplasmic organelles become concentrated in cell centers within rings of microtubules and masses of microfilaments. Questions were raised about this process and its contractile nature by studies demonstrating that platelet microtubules several minutes later in new locations. Earlier invesigations showed that Taxol, a microtubule-stabilizing agent, did not inhibit platelet shape change, internal transformation, secretion, aggregation, or clot retraction. The diameters of microtubule coils in discoid platelets treated or nor treated with Taxol and in platelets activated by thrombin, ADP and a foreign surface were measured. No significant differences in diameters of microtuble rings were found in control or Taxol-treated cells. After activation by ADP, thrombin, or the grid surface, the diameter of coiled microtubules decreased by 30% or more. The concept that internal transformation is a contractile event, is evidently supported.