Effect of magnesium sulfate on platelet deposition in rabbits following temporary arterial occlusion with surgical clips.

The effect of magnesium sulfate on thrombus formation in vivo was studied by scanning electron microscopy utilizing the model of endothelial damage by temporary arterial occlusion with a Heifetz clip. Examination of arterial segments compressed by the surgical clip for 30 minutes, followed by 2 hours of reflow, revealed marked attachment of platelets and deposition of erythrocytes, with very few leukocytes, to exposed subendothelial tissues. This thrombotic deposition protruded as much as 150 mu into the vascular lumen (15% of luminal diameter). By contrast, in animals pretreated with magnesium sulfate, this deposition was limited to isolated areas of single or very few platelets with few erythrocytes or leukocytes. The difference in overall quantity of thrombus formation between nontreated and magnesium sulfate-treated groups was much less obvious after 24 hours; however, fewer leukocytes and erythrocytes were seen to be attached to the platelet carpet in the treated group as compared with the nontreated group. The effect of magnesium sulfate on the overall quantity of thrombus formation corresponded inversely to the measured levels of serum magnesium in these groups.