Summary
The in vitro effect of magnesium (Mg) on platelet aggregation and platelet release
function was evaluated in healthy volunteers. Platelet aggregation was induced with
collagen, ADP, or thrombin after incubation of the sample with saline or increasing
concentrations of magnesium sulphate (MgSO4) (0.5-8.0 mM). Mg showed a dose-dependent inhibition of platelet aggregation in whole
blood, platelet rich plasma and washed platelets. An antiaggregatory effect was also
present with low Mg concentrations. Statistically significant inhibition of the mean
aggregation response was obtained in 83% of the different media and agonists tested
following the addition of 1.0 mM Mg. The remaining 17% were significantly inhibited
with the addition of 2.0 mM Mg. The platelet synthesis of thromboxane A2 and release of beta-thrombo-globulin were also inhibited by Mg, in a dose-dependent
manner. In order to evaluate if any of these effects were modified by conventional
antithrombotic treatment with low-dose acetylsalicylic acid (ASA), volunteers were
asked to meet on two consecutive days. On day 2 the participants were given 300 mg
ASA orally, one hour prior to blood sampling. The Mg mediated effects were present
independent of this pretreatment with ASA. Following stimulation with collagen a synergistic
effect of Mg and ASA was demonstrated on platelet aggregation. The platelet inhibiting
effect demonstrated in this study may in part explain the beneficial effect of Mg
infusion in some patients with acute myocardial infarction. The effect of Mg infusion,
given alone or administered simultaneously with ASA, should also be evaluated in other
arterial thrombotic disease states.
