These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The kinetics of changes in intracellular calcium concentration in fura-2-loaded human platelets.
    Author: Sage SO, Rink TJ.
    Journal: J Biol Chem; 1987 Dec 05; 262(34):16364-9. PubMed ID: 3119586.
    Abstract:
    We have investigated the sub-second kinetics of changes in cytosolic free calcium, [Ca2+]i, in fura-2-loaded human platelets by stopped-flow fluorimetry. Thrombin, vasopressin, platelet-activating factor, and the thromboxane A2 analogue U46619 all evoked a rise in [Ca2+]i which was delayed in onset by 200-400 ms in the presence of 1 mM external Ca2+. The responses to these agonists in media containing 1 mM EGTA or 1 mM Ni2+, to prevent Ca2+ influx, were delayed by an additional 60-100 ms. These results indicate that agonist-evoked Ca2+ influx precedes the release of Ca2+ from internal stores. The delays in onset of both responses are sufficient for one or more biochemical steps to lie between ligand-receptor binding and Ca2+ flux generation. ADP responses in media containing EGTA or Ni2+ were similar to those evoked by other agonists, but the response in the presence of external Ca2+ was markedly shorter, occurring without measurable delay at optimal ligand concentration. Analysis of this response showed some delay in ADP-evoked influx at lower concentrations, but this delay was markedly less than that observed with thrombin at doses giving the same elevation in [Ca2+]i. These results suggest that ADP evokes influx using a different transduction system, more closely coupled to the Ca2+ entry system than that used by other agonists. Differences between thrombin- and ADP-evoked influx were further demonstrated by the inhibitory actions of cAMP, which reduced and substantially increased the delay in onset of thrombin-evoked influx but did not measurably delay the influx evoked by an optimal concentration of ADP.
    [Abstract] [Full Text] [Related] [New Search]