Subsecond calcium dynamics in ADP- and thrombin-stimulated platelets: a
continuous-flow approach using indo-1
GD Jones and AR Gear
Department of Biochemistry, University of Virginia, Charlottesville 22908.
The regulation and kinetics (less than 5 seconds) of cytosolic calcium
changes ([Ca2+]i) in stimulated blood platelets have been investigated
under physiological blood flow conditions. Using a newly-developed
continuous-flow approach with indo-1-loaded human platelets, adenosine
diphosphate (ADP, 10 mumol/L) and thrombin (5 U/mL) were equally effective
in significantly increasing [Ca2+]i by 0.5 seconds. ADP induced a transient
[Ca2+]i peak of 1 to 2 mumol/L near 2 seconds, whereas thrombin caused a
sustained and larger response. The first phase (less than 2 seconds) was
not influenced by a lack of extracellular Ca2+, in contrast to the
subsequent [Ca2+]i increase that only reached about 0.7 mumol/L for either
ADP or thrombin. The shear rates used in our continuous-flow apparatus were
physiological (less than 1,258 sec-1) and only slightly increased the basal
[Ca2+]i of 0.1 mumol/L. Platelet aggregation (less than 5 seconds),
assessed by single- particle counting, was not altered in platelets loaded
with indo-1/AM (2.5 mumol/L).
Volume 71,
Issue 6,
pp. 1539-1543,
06/01/1988
Copyright © 1988 by The American Society of Hematology
