Spatial distribution and temporal change of cytoplasmic free calcium in human platelets.
Our digital imaging microscope equipped with a microspectrofluorometer revealed in single resting human platelets the existence of continuous Ca2+ gradient increasing towards the plasma membrane (frequency; 100%) and discontinuous ones (Ca2+ plateaus) in the endoplasmic regions (frequency: 70%). An average cytoplasmic free Ca2+ concentration ([ Ca2+]i) in a whole cytoplasm was 72 +/- 7 nM, ranging from 30 nM in the lowest to 150 nM in the highest region just beneath the plasma membrane. When stimulated with thrombin, [Ca2+]i uniformly increased to the average [Ca2+]i of 300 nM and these gradients disappeared. This [Ca2+]i transient was followed by the sustained increase in [Ca2+]i in both single cells and cell suspension.
Tsunoda
Y
Y
Department of Physiology, Kansai Medical University, Osaka, Japan.
Matsuno
K
K
Tashiro
Y
Y
D001792:Blood Platelets / Q000032:analysis*; D002118:Calcium / Q000097:blood*; D002462:Cell Membrane / Q000032:analysis; D003593:Cytoplasm / Q000032:analysis*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D010974:Platelet Aggregation / Q000187:drug effects; D012701:Serotonin / Q000032:analysis / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013917:Thrombin / Q000494:pharmacology
D012701:Serotonin; D013917:Thrombin; D002118:Calcium