Cell death and expression of heat-shock protein Hsc70 in the hyperthermic rat brain.

Stressful stimuli induce two distinct cellular reactions, the heat-shock (stress) response and programmed cell death. This study utilizes a dual procedure involving immunocytochemistry for heat-shock protein localization and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay for localization of cell death at the cellular level. Whole-body hyperthermia resulted in cell death in the adult rat thymus and testis with a robust signal seen in the testis. Distinct populations of constitutively expressed Hsc70-positive cells and TUNEL-positive cells were apparent. Cellular layers that exhibited high levels of Hsc70 were not triggered into cell death by the thermal stress. High expression of Hsc70 was observed in neuronal populations in the dentate gyrus, CA1 and CA2 region of the hippocampus and Purkinje neurons of the cerebellum. Hyperthermia-induced cell death was not observed in these neuronal cell types, suggesting that neuronal expression of constitutive Hsc70 may play roles in preprotecting neurons from stressful stimuli.