Myocardial infarction induces expression of midkine, a heparin-binding growth factor with reparative activity.

We examined midkine (MK) expression in the rat heart upon experimental myocardial infarction. Immuno-histochemical staining revealed, 6 hours after ligation of the left anterior descending coronary artery, strong MK immuno-reactivity in myocytes and endothelial cells of a non-infarcted cardiac region. The myocytes of the infarcted cardiac region destined for death showed only a little immunoreactivity. Northern blot analysis suggested that the increased immunoreactivity was due to increased MK synthesis. The induced MK expressionis likely to mimic the expression during embryogenesis: MK was strong lyexpressed in the myocytes of embryonic heart, and the expression decreased during embryogenesis.