title: On the significance of the influx of calcium ions into stimulated human blood platelets.
abstract: Blood platelets, upon stimulation with various substances, take up calcium ions from the suspending medium. This influx occurs simultaneously with the release reaction, i.e. the specific secretion of a variety of substances from storage organelles and the second wave of aggregation. Various inhibitors of the release reaction inhibit this Ca2+ influx. Platelets previously loaded with 45Ca show an increased efflux of the cation upon stimulation by thrombin. These results suggest that the plasma membrane acquires an increased permeability to Ca2+ only in a later phase of platelet activation, in most cases after the earlier release of Ca2+ into the cytoplasm from Castoring organelles. Rapid shape change and release proceed independently of external calcium, whereas clot retraction depends upon a prolonged increased permeability of the plasma membrane to this cation.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D001693:Biological Transport, Active; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D003094:Collagen / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D010974:Platelet Aggregation / Q000187:drug effects; D012701:Serotonin / Q000097:blood; D013917:Thrombin / Q000494:pharmacology
chemical_list: D012701:Serotonin; D000244:Adenosine Diphosphate; D003094:Collagen; D004492:Edetic Acid; D013917:Thrombin; D002118:Calcium; D004837:Epinephrine