Role of cytoplasmic calcium in platelet aggregation.
BACKGROUND
Although adherence and aggregation of platelets on an active surface such as exposed subendothelial matrix or foreign surfaces is integral to the occlusion of blood vessels, its mode of action is not fully understood.


METHODS
The role of cytoplasmic ionized Ca(2+) concentration ([Ca(2+)](i)) in platelet activation induced by contact with a glass surface under shear-stress was studied by employing confocal laser scanning microscopy (CLSM) in conjunction with a parallel plate flow chamber. Changes in [Ca(2+)](i) and morphology of aggregating platelets on glass surface was simultaneously examined.


RESULTS
Under static condition, contact with glass caused platelet adhesion to the surface, which was associated with [Ca(2+)](i) rise and morphological change; however, platelets did not develop a large aggregation on the surface. Under lower shear-stress, the number of the single platelets adsorbed on the surface was less than that under static condition. Although shear-stress increased the number of single platelets involved and enhanced morphological change in aggregating platelets in a shear-stress related manner, the peak [Ca(2+)](i) value in individual platelets were not increased.


CONCLUSIONS
These observations may suggest the crucial roles of shear-stress in platelet aggregate formation at the site of arterial stenosis. Shear-stress might enhances platelet aggregate growth not through the enhancement of [Ca(2+)](i) rise.
Department of Surgery II, Osaka University Medical School, Osaka, Japan. ariyoshi@surg2.med.osaka-u.ac.jp
H
H
Ariyoshi
Y
Y
Aono
Y
Y
Tsuji
A
A
Ueda
M
M
Tokunaga
K
K
Uchide
M
M
Sakon
M
M
Monden
D002118:Calcium / Q000502:physiology*; D005260:Female; D018056:Hemorheology; D006487:Hemostasis / Q000502:physiology; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D010974:Platelet Aggregation
D002118:Calcium