Microtubule reassembly in surface-activated platelets
JG White, M Krumwiede and JJ Sauk
It is generally accepted that a circumferential microtubule supports the
discoid shape of resting platelets. The fate of the many-coiled polymer
following platelet activation, however, has been a subject of considerable
debate. Morphological investigations have suggested that the
circumferential coils are constricted into tight rings around centrally
concentrated organelles during platelet shape change. Biochemical studies
employing colchicine-binding assays, on the other hand, have indicated that
the bundle of microtubules dissolves almost completely within seconds after
activation and reassembles in a new location one to four minutes later. The
present study has accepted the latter hypothesis in order to examine the
second part of the disassembly-reassembly theory proposed in biochemical
studies. Platelets exposed to low temperatures sufficient to remove all
microtubules were placed on glass slides and microscope grids to cause
surface activation during rewarming. The combined stimuli of rewarming and
surface activation might have been expected to cause more rapid assembly
than warming alone or activation alone. This was not the case. Reassembly
of microtubules during rewarming and simultaneous surface activation was
not accelerated. In contrast to the constriction of microtubule rings
observed during activation in control platelets, the diameters of coils
that developed in chilled platelets one to two hours after rewarming and
surface activation were twice those of control cells.
Volume 65,
Issue 6,
pp. 1494-1503,
06/01/1985
Copyright © 1985 by The American Society of Hematology
