Ouabain Increases the Calcium Concentration in Intracellular Stores Involved in Stimulus-Response Coupling in Human Platelets

• Published in: Circulation research Vol. 67; no. 6; pp. 1494 - 1502
• Main Authors: Roevens, Peter, de Chaffoy de Courcelles, Didier
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01-12-1990; Lippincott
• Subjects: Aminoquinolines; Biological and medical sciences; Blood Platelets - drug effects; Blood Platelets - metabolism; Calcium - blood; Calcium - metabolism; Chlortetracycline; Enzyme Activation; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Homeostasis; Humans; Ouabain - pharmacology; Sodium - metabolism; Stimulation, Chemical; Thrombin - pharmacology; Type C Phospholipases - metabolism; Vertebrates: blood, hematopoietic organs, reticuloendothelial system; Human; Calcium; Radiolabelling; Electrophysiology; Fluorescence; Homeostasis; Ions; Blood; Platelet; Storage; Cations; Intracellular; Response stimulus relation
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.RES.67.6.1494

The effect of ouabain on Ca homeostasis in human platelets was studied using both quin 2 and chlorotetracycline to monitor changes in cytosolic Ca as well as changes in the amount of Ca accumulated in intracellular storage sites. In resting platelets, ouabain induces a concentration- and time-dependent increase in cytosolic Ca concentration and a marked elevation of Ca in the intracellular stores. The amount of Ca mobilized from these stores upon stimulation with thrombin, as well as thrombin-induced secretion of platelet 5-hydroxytryptamine, was increased after preincubation with the glycoside (3×10 M). These data show that ouabain induces an elevation of intracellular Ca levels, most likely mediated via Na-Ca exchange, and that this incremental amount of Ca is accumulated in an intracellular store involved in stimulus-response coupling. This may explain the enhanced functional responses of platelets to agonists in the presence of ouabain and suggests a role for Na-Ca exchange in Ca homeostasis of the human platelet.