|
|||||||||
|
|
|
|
|
|
|
|
|
|
|
L Ebbeling, C Robertson, A McNicol and JM Gerrard
Department of Paediatrics, University of Manitoba, Winnipeg, Canada.
The dense tubular system (DTS) functions to regulate platelet activation by
sequestering or releasing calcium, similar to the sarcotubules of skeletal
muscle. In resting platelets, the DTS exists as thin elongated membranes.
Within 10 seconds of the addition of thrombin, platelets show a major
ultrastructural change in their DTS: from the thin elongated form to a
rounded vesicular form. These morphologic changes were demonstrated with
two different stains and two different fixation methods. Platelets exposed
to the calcium ionophore A23187 showed the same ultrastructural changes in
the DTS. In contrast, the DTS remains in a thin elongated form when
platelets are stimulated by the protein kinase C activators phorbol
12-myristate 13-acetate (PMA) and oleoylacetylglycerol (OAG). These
morphologic changes may be related to the discharge of calcium from the DTS
because this is stimulated by thrombin and A23187, but not by PMA.
Preincubation of the platelets with the intracellular calcium chelator
5,5'-dimethyl-bis-(0- aminophenoxy)-ethane-N,N,N',N tetra acetic acid
(BAPTA) largely prevented both the thrombin-induced rise in intracellular
calcium and the changes in DTS morphology, suggesting that the changes in
DTS morphology are secondary to the increase in cytosolic calcium. The
results provide a morphologic correlate to existing biochemical evidence
showing that the DTS is involved early during paltelet activation.
This article has been cited by other articles:
| |||||||||||
 |
 |
 |
|||||||
 |
 |
 |
 |
 |
 |
 |
 |
||
| Copyright © 1992 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
