Summary
Magnesium deficiency and its association with platelet hyperreactivity has been well
recognised in a variety of diseases including myocardial infarction, preeclampsia,
and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding
time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition,
the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and
on surface expression of GMP-140 or GP53 was evaluated. Mg2+(4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly,
independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine,
thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced
by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression
of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p <0.05) by
40% and binding of Fg or surface expression of GMP-140 by 30% (p <0.05). Thus, pharmacological
concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.
