ENHANCEMENT OF HEAT-SHOCK-PROTEIN EXPRESSION AFTER TRANSIENT ISCHEMIAIN THE PRECONDITIONED SPINAL-CORD OF RABBITS

Purpose: This investigation was designed to evaluate the mechanism use d to acquire a tolerance to spinal ischemia. We investigated induction s of the heat shock protein (HSP) 70 gene and protein in rabbit spinal cord with or without preconditioning. Methods: Neurologic function, m orphologic changes, and inductions of HSP70 messenger RNA (mRNA) and p rotein were compared in the cases of a 15-minute ischemia 2 days after sham treatment and a 15-minute ischemia 2 days after 10-minute precon ditioning. Result: HSP70 mRNA was induced at 8 hours of reperfusion af ter a 15-minute ischemia 2 days after sham treatment. HSP70 protein wa s induced slightly in selective motor neuron cells at 8 hours of reper fusion, and about 70% of motor neuron cells showed selective cell deat h after 7 days of reperfusion (p < 0.01). On the other hand, large pop ulations of the motor neuron cells survived at 7 days after the 15-min ute ischemia that was applied at 2 days after preconditioning (p < 0.0 1). HSP70 mRNA was induced persistently as compared with the case of a 15-minute ischemia 2 days after sham treatment. The motor neuron cell s strongly produced immunoreactive HSP70 from 8 hours to 2 days. Concl usion: Preconditioning with 10-minute ischemia enhanced and prolonged the HSP70 gene expression at both mRNA and protein levels and saved th e motor neuron cells from subsequent lethal ischemia. These changes of HSP70 gene expression may play an important role in the acquisition o f ischemic tolerance of motor neuron cells in rabbit spinal cord.