Cytoplasmic free Ca2+ in human platelets: Ca2+ thresholds and Ca‐independent activation for shape‐change and secretion
- 1 November 1982
- journal article
- Published by Wiley in FEBS Letters
- Vol. 148 (1) , 21-26
- https://doi.org/10.1016/0014-5793(82)81234-9
Abstract
Cytoplasmic free [Ca2+], [Ca2+]i, was measured in human platelets using the intracellularly‐trapped, fluorescent indicator quin2. Basal [Ca2+]i with the Ca2+‐ionophore ionomycin revealed apparent thresholds for shape‐change, 5‐HT release and aggregation of approx. 0.5μM, 0.8μM and 2 μM. Thrombin raised [Ca2+]i to 3 μM fast enough for the Ca2+ to have triggered the cell activation. However, thrombin released more 5‐HT than ionomycin could, and in Ca2+‐free medium thrombin evoked shape‐change and secretion even when [Ca2+]i remained near basal levels throughout, suggesting the existence of alternative triggers for shape‐change and secretory exocytosis.Keywords
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