Effects of simulated weightlessness on liver Hsp70 and Hsp70mRNA expression in rats

Space flight is known to induce a number of hepatic physiological alterations. In this study, we investigated Hsp70 expressing features of rat liver under simulated weightlessness. Tail-suspension was used to simulate the weightlessness animal model. Forty-eight male Wistar rats were randomly assigned to 6 experimental groups and Hsp70 protein and mRNA expressions in the liver were detected by Western blot and RT-PCR respectively. The tail-suspension significantly increased Hsp70mRNA expression levels in rat liver (P<0.05). The semi-quantitative PCR showed that Hsp70mRNA was upregulated as early as 6 hours of suspension. Western blot analysis indicated that Hsp70 protein was significantly upregulated in the early stage of suspension as compared with controls (P<0.05). The results suggest that simulated weightlessness acts as a kind of stress to elevate liver Hsp70 expression both at protein and mRNA levels. This may be meaningful in astronaut's trainings by preadaptation to non-damaging stress exposures or other environmental factors to foster the astronaut's ability of weightless tolerance.