MIDKINE IS PRESENT IN THE EARLY-STAGE OF CEREBRAL INFARCT

Expression of midkine (MK), a growth factor with neurotrophic activiti es, was examined immunohistochemically in experimental cerebral infarc t of rats. From postoperative day 1 to day 7 after the onset of infarc t, anti-MK immunoreactivity was observed in the surrounding ischemic z one of the infarct but not in the necrotic lesion. The immunoreactive material was identified to be MK by Western blotting. On day 14, anti- MK immunoreactivity became negative. Absence of MK in the normal brain was verified both by immunohistochemical staining and Western blottin g. The induced expression of MK is an early event: increased expressio n of glial fibrillary acidic protein (GFAP), a marker of astrocytes, s tarted on day 4 and continued to day 14. These findings suggest that M K is produced around the site of nerve damage and plays a role as a re parative neurotrophic factor during the early phase of cerebral infarc t.