Calcium mobilization in density subpopulations of rabbit washed platelets
Majima, M.; Li, B.Y.; Huang, A.; Katori, M.
International Journal of Tissue Reactions 17(2): 51-60
1995
ISSN/ISBN: 0250-0868 PMID: 8847181 Document Number: 449370
To estimate the responsiveness of an individual platelet, rather than a group of platelets, we determined the intracellular calcium concentration ((Ca-2+)-i) of single platelets using digital imaging microscopy after density fractionation. The mean (Ca-2+)-i of non-fractionated resting single platelets was 74.0 +- 4.2 nM (n = 71). Immediately after thrombin stimulation (100 U/ml), (Ca-2+)-i increased markedly in the entire cytoplasm, reaching maximum levels of 400-1000 nM, and decreased slightly thereafter. These maximum levels varied markedly from cell to cell in non-fractionated platelets. Although there was no significant difference in the resting levels of (Ca-2+)-i of single platelets even after density fractionation, the peak (Ca-2+)-i levels after thrombin stimulation (10 and 100 U/ml) in platelets with higher density ( gt 1.062) were significantly higher than those in platelets with intermediate density (1.052-1.061) or lower density ( lt 1.051). This higher responsiveness of higher-density platelets in calcium mobilization was accompanied by higher aggregability and higher reactivity in the release reaction. These results suggest that higher responsiveness in higher-density platelets may be explained by the higher reactivity in (Ca-2+)-i mobilization.