INDUCTION OF HEAT-SHOCK HSP70 MESSENGER-RNA AND HSP70-KDA PROTEIN IN NEURONS IN THE PENUMBRA FOLLOWING FOCAL CEREBRAL-ISCHEMIA IN THE RAT

Induction of hsp70 heat shock protein (HSP70) and hsp70 mRNA was exami ned using adjacent sections in the same rat brain following permanent middle cerebral artery (MCA) occlusions. hsp70 mRNA was induced within 4 h of MCA occlusion and persisted for at least 24 h. Cellular resolu tion autoradiographs suggested that hsp70 mRNA was induced primarily i n neurons in the periphery of ischemia both outside and inside of the infarction, with small amounts of hsp70 mRNA being induced in the core of the infarction. HSP70 protein was localized in neurons outside the infarction and in endothelial cells within the infarction at 24 h but not at 4 h following permanent MCA occlusions. It is proposed that th e penumbra, one of the areas that can be rescued by pharmacological ag ents, can be defined anatomically as the volume of tissue outside the area of infarction in which HSP70 protein is expressed primarily in ne urons.