The upregulation of cognate and inducible heat shock proteins in the anoxic turtle brain.

Because heat shock proteins (HSPs) have an important protective function against ischemia/anoxia in mammalian brain, the authors investigated the expression of Hsp72 and Hsc73 in the anoxia-surviving turtle brain. Unlike the mammalian brain, high levels of Hsp72 were found in the normoxic turtle brain. Hsp72 levels were significantly increased by 4 hours of anoxia, remained constant until 8 hours, and then decreased to baseline at 12 hours. By contrast, Hsc73 was progressively increased throughout 12 hours of anoxia. This differential expression suggests different protective roles: Hsp72 in the initial downregulatory transition phase, and Hsc73 in maintaining neural network integrity during the long-term hypometabolic phase.