产前缺氧性适应后胎鼠、新生大鼠脑内凋亡相关基因bcl-2、bax mRNA的表达

The expression of apoptosis-related gene bcl-2 and bax mRNA in the brain cells of fetal and newborn rat after prenatal hypoxic adaptation

目的 通过观察产前缺氧性适应后胎鼠、新生大鼠脑内bcl-2和bax基因mRNA变化,探讨产前缺氧性适应对胎鼠、新生鼠脑保护作用机制。方法 将临产前Wistar孕大白鼠24只随机分成2组,I组为实验组（缺氧性适应组）,Ⅱ组为对照组。两组于缺氧性适应（Ⅱ组模拟）后1、3、8、24、48、72、120、168h各取7只胎鼠或新生鼠断头取脑,分别做bcl-2、bax mRNA测定。结果 1.正常胎鼠、新生鼠脑组织中即有bcl-2和bax表达,从宫内22d到生后第7d,bcl-2、bax基因表达、及bcl-2/bax比值无明显变化,2.缺氧性适应后 8h bax基因表达即有减少,24h降低最为明显,可持续至120h;缺氧性适应后24h bcl-2基因表达开始增加,可持续至72h;bcl-2/bax比值缺氧性适应后8h开始增加,24h达高峰,可持续至72h。结论 产前缺氧性适应后胎鼠、新生鼠脑组织bcl-2基因表达增加,bax基因表达减少,bcl-2/bax比值增加,此变化有时间依从性。

Objective To investigate the mechanism involved in the brain protection afforded by prenatal hypoxic adaptation by determining the quantitative variation in bcl-2 and bax mRNA expression.Methods Twenty-four Wistar pregnant (22d pregnant) rat were randomly divided into two groups: group I (hypoxia group) and group *** ( control group) . In group Ⅰ the pregnant rats were placed in an airtight cabin specially designed for hypoxic adaptation. When O2 % in the cabin decreased to 15%, the animals were taken out breathing fresh air for 5min and then placed back in the cabin and underwent another episode of hypoxia. In group Ⅱ the animals were placed in the cabin which was not tightly closed and underwent no hypoxia. 7 fetal or newborn rats were taken at 1st, 3rd, 24th, 48th, 72nd, 120th, and 168th h after prenatal hypoxic adaptation from each group and their brains removed for determination of bcl-2 mRNA and bax mRNA. Results In control group the expression of bcl-2 and bax were observed in the brain tissue of normal fetal or newborn rats from the 22nd day in the uterus to the 7th day postpartum during which there were no significant changes in bcl-2 gene expression while bax gene expression gradually decreased with time ( the decrease was of no statistical significance) . In hypoxia group bax gene expression decreased at 8th h after hypoxic adaptation and reached the bottom at 24th h which persisted until 120th h; while bcl-2 gene expression started increasing at 24th h after hypoxic adaptation and persisted until 72nd h. The bcl-2/bax ratio also started increasing at 8th h after hypoxic adaptation and peaked at 24th h and persisted until 72nd h. Conclusions In the brain tissue of fetal and newborn rats which have undergone prenatal hypoxic adaptation, bcl-2 gene expression is elevated, bax gene expression decreases and bcl-2/bax ratio increases. These changes are time -dependent.