低G重复暴露对大鼠脑热休克蛋白70表达水平的影响

目的 通过低G重复暴露的预适应作用，来诱导热休克蛋白70（HSP70）表达，以探讨预刺激的适宜强度。方法 SD大鼠80只，随机分为正常对照组（5只）和＋4Gz重复暴露（＋4Gz/3min,3次／d)1d、3d和5d组（每组25只），分别于暴露后6h、1d、2d、4d和6d处死取脑，做冰冻切片，进行免疫组织化学染色，观察HSP70的表达水平。结果 各实验组＋4Gz/3min重复暴露后HSP70在皮层、海马、丘脑和丘脑下部等部位的表达均有明显的时相特点。暴露后6h各部位均有轻中度的HSP70阳性反应，暴露后1d表达至峰值，2－3d后开始明显减弱。从表达部位看，HSP70阳性反应在顶叶皮层、梨状皮层和丘脑下部表达较强，丘脑次之，海马较弱。各组HSP70表达峰值呈均在暴露后1d，但暴露1d组2d后强度明显减弱，而暴露3－5d组在2d后仍然维持较高水平，即除海马外，各脑区在暴露后第6天仍有较高的表达，均未恢复至正常对照水平。结论 多天低G重复暴露诱导的HSP70表达较1d重复暴露组的表达更强，持续时间更长。

The influence of repeated +Gz exposures on HSP70 expression in rat brain

Objective To explore the suitable intensity of repeated low +G z adaptation exposure in order to induce the highest heat shock protein 70(HSP70) expression in rat brain. Methods Eighty SD male rats were randomly divided into control group (5 rats), +4 G z exposures (+4 G z/3 min,3 times/day) one day, three days and five days group (each group 25 rats). The expression levels of HSP70 in rat brain were measured by immunohistochemistry staining 6 hours, 1 day, 2 days, 4 days, 6 days after last exposure. Results The HSP70 expression levels after repeated +4 G z exposures had obvious phasic characteristics in cortex, hippocampus, thalamus and hypothalamus. The expression level of HSP70 6 hours after exposure was weak, it reached peak value 1 day after exposure, and began lowering down 2 or 3 days after the exposures. The expression level of HSP70 was strongest in parietal cortex, piriform cortex and hypothalamus, strong in thalamus, and relatively weak in hippocampus. In all 3 experimental groups, the HSP70 expression reached peak value 1 day after last exposure, but it was obviously weakened 2 days after exposures in 1 day group, while in 3 days and 5 days group it maintained on a high level and it did not return to normal value 6 days after last exposure. Conclusion The results indicated that the level of HSP70 expression after repeated +4 G z exposures for several days were stronger, and its sustaining time was longer than those of single day exposure group.