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Factor VIII-von Willebrand factor requires calcium for facilitation of platelet adherence

K S Sakariassen, M Ottenhof-Rovers, J J Sixma

    Blood
    |May 1, 1984
    PubMed

    Insights

    Divalent cations like calcium (Ca2+) and magnesium (Mg2+) are crucial for platelet adherence to damaged arteries. Calcium is essential for platelet spreading and activating factor VIII-von Willebrand factor (FVIII-vWF) for optimal adherence.

    Area of Science:

    • Hematology
    • Biochemistry
    • Vascular Biology

    Background:

    • Platelet adherence to damaged blood vessels is a critical step in hemostasis and thrombosis.
    • Divalent cations, particularly calcium (Ca2+), are known to play a role in various biological processes, including cell adhesion.
    • The specific roles of different divalent cations in platelet-subendothelium interactions under flow conditions require further elucidation.

    Purpose of the Study:

    • To investigate the distinct roles of divalent cations, specifically calcium (Ca2+) and magnesium (Mg2+), in mediating platelet adherence to deendothelialized human arteries.
    • To determine the influence of Ca2+ and Mg2+ on platelet spreading and the function of factor VIII-von Willebrand factor (FVIII-vWF) in supporting platelet adhesion under flow.

    Main Methods:

    • Utilized an annular perfusion chamber to simulate flowing blood conditions.
    • Investigated platelet adherence to deendothelialized human artery segments.
    • Manipulated concentrations of free Ca2+ and Mg2+ ions in perfusates and assessed platelet spreading and adherence.

    Main Results:

    • Platelet spreading on the subendothelium was significantly impaired at free Ca2+ concentrations below 30 microM.
    • Replacing Ca2+ with Mg2+ did not alter adherence in the absence of exogenous FVIII-von Willebrand factor (FVIII-vWF).
    • However, Mg2+ could not substitute for Ca2+ in supporting FVIII-vWF-mediated platelet adherence; bound FVIII-vWF required Ca2+ exposure for optimal activity.

    Conclusions:

    • Divalent cations play at least two distinct roles in supporting platelet adherence.
    • Ca2+ or Mg2+ is required for platelet spreading on the subendothelium.
    • Ca2+ is essential for the optimal biologic activity of FVIII-vWF in mediating platelet adherence to the vessel wall.

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