title: Regulation of cytosolic calcium by collagen in single human platelets.
abstract: 1. There is controversy in the literature as to whether collagen is able to induce directly a rise in cytosolic calcium concentration ([Ca2+]i) in human platelets. We have addressed this question by observing the cytosolic calcium response of single fura-2-loaded human platelets settling onto a collagen-coated surface using dynamic fluorescence ratio imaging. 2. Following a short lag phase after adherence to collagen fibres, platelets underwent a rapid rise in cytosolic calcium from basal values of 80 +/- 13 nM (n = 24) to a peak of 475 +/- 42 nM (n = 24) which was sustained for the remaining period of the experiment. 3. The tyrphostin protein tyrosine kinase inhibitor, ST271, reduced substantially the proportion of platelets which exhibited a rise in [Ca2+]i on adherence to collagen and transformed the response in remaining cells to one of oscillations. 4. In contrast, and as a control for collagen, laminin-coated surfaces induced adherence of human platelets without elevating intracellular [Ca2+]; the cells however remained responsive to ADP. 5. We conclude that collagen directly induces a rise in cytosolic calcium in single human platelets through a tyrosine kinase-mediated pathway.
authors.affiliation: University Department of Pharmacology, Oxford.
authors.forename: A W
authors.initials: AW
authors.lastname: Poole
authors.forename: S P
authors.initials: SP
authors.lastname: Watson
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D003094:Collagen / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000096:biosynthesis; D007797:Laminin / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013343:Styrenes / Q000494:pharmacology
chemical_list: D007295:Inositol Phosphates; D007797:Laminin; D013343:Styrenes; C086531:ST 271; D000244:Adenosine Diphosphate; D003094:Collagen; D011505:Protein-Tyrosine Kinases; D002118:Calcium