MARKED ALTERATIONS IN THE CELLULAR-LOCALIZATION AND LEVELS OF APOLIPOPROTEIN-E FOLLOWING ACUTE SUBDURAL-HEMATOMA IN RAT

Apolipoprotein E (apoE) plays a role in the response to acute brain in jury, the mechanisms as yet remain unknown. In the present study, alte rations in the immunohistochemical localisation of apoE in rat cortex were examined at 30 min, 2 h or 4 h following production of an acute s ubdural haematoma, Levels of apoE were determined in cortex by immunob lotting at 30 min and 4 h post-haematoma. Extensive areas of ischaemic cell damage were observed in the cortex underlying the haematoma with minimal damage observed in shams. In sham animals, apoE immunoreactiv ity was confined to astrocytes and their processes. Following the haem atoma induction, apoE immunoreactivity was dramatically altered. At 30 min post-haematoma, intense apoE staining was observed in clusters of neuronal perikarya and the neuropil throughout the cortical layers un derlying the haematoma and this persisted at 2 h and 4 h post-haematom a. Additionally, at 4 h post-haematoma marked apoE staining of discret e foci within the neuropil closely associated with capillaries was con sistently observed in the ipsilateral cortex. Immunoblotting indicated there were no significant alterations in the cortical levels of apoE at 30 min post-haematoma but, at 4 h post-haematoma, there was a signi ficant elevation (27%, P < 0.001) in the levels of apoE in cortex unde rlying the haematoma compared to control levels. The results indicate that following acute subdural haematoma, a rapid cellular redistributi on of apoE occurs and precedes a significant elevation in the levels o f apoE. These alterations in apoE may occur, at least initially, as pa rt of the brain's protective response to injury. (C) 1997 Elsevier Sci ence B.V.