Patterns of growth inhibitory factor (GIF) and glial fibrillary acidic protein relative level changes differ following left middle cerebral artery occlusion in rats

Growth inhibitory factor (GIF) has been identified as a new metallothionein-like protein, the level of which is decreased in the Alzheimer's disease brain. GIF and glial fibrillary acidic protein (GFAP) have been reported to be expressed in reactive astrocytes in the rat brain following stab wounds. Moreover, strong expression of GIF mRNA in reactive astrocytes after ventricular injection of kainic acid has been demonstrated. To clarify the biological functions of GIF and GFAP in repair of the CNS, we examined changes in their relative levels to sham control using a Western blotting technique in the rat left hemisphere following occlusion of the left middle cerebral artery, for 28 days after surgery. The GIF relative level declined to 56% of the sham-operated control value on day 7. Thereafter the GIF relative level increased and returned to the normal relative level by days 21–28. The GFAP relative level increased from day 3 and reached a maximum of 120% of the sham-operated control value on days 14–21. While GIF and GFAP were both detected in reactive astrocytes, an increase in the GFAP relative level occurred prior to an increase in GIF relative level following the ischemia. The patterns of changes in relative expression levels of GIF and GFAP were quite similar to those in our previous studies on effects of cerebral stab wounds in rats, although the changes were more rapid in the previous studies. GIF and GFAP appear to play different roles in the repair of the CNS. The present results also indicated that GIF could play an important role in CNS repair after cerebral ischemia and provide new insights into the mechanism of gliosis investigated mainly from the viewpoint of GFAP.