Monitoring of the activation of receptor-operated calcium channels in human platelets.
Activation of receptor-operated calcium channels has been monitored by measurements of the quenching of the fluorescence of intracellularly trapped fura-2 by Mn entering from the extracellular medium. Release of calcium from intracellular stores was followed simultaneously by measurements of the ratio of the fluorescence excited at 340 and 380 nm. Thrombin, ADP, platelet-activating-factor (PAF) and collagen, all produced both release of calcium from the intracellular stores and uptake of Mn from the extracellular medium. The uptake of Mn, but not the increase of (Ca2+)i, was blocked by nickel. These results suggest the existence of plasma membrane calcium channels which can be activated by the different agonists tested here. The activation of calcium channels was very fast and transient with ADP and PAF, fast and maintained with thrombin, and delayed with collagen.
Alonso
M T
MT
Departmento de Fisiología y Bioquímica, Facultad de Medicina, Universidad de Valladolid, Spain.
Sanchez
A
A
García-Sancho
J
J
D000244:Adenosine Diphosphate; D001792:Blood Platelets / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D003094:Collagen; D006801:Humans; D010972:Platelet Activating Factor; D010974:Platelet Aggregation; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013050:Spectrometry, Fluorescence; D013917:Thrombin
D015220:Calcium Channels; D010972:Platelet Activating Factor; D011956:Receptors, Cell Surface; D000244:Adenosine Diphosphate; D003094:Collagen; D013917:Thrombin