镉对小鼠精子和生精细胞超微结构及生精细胞bcl-2、bax基因表达的影响

Effects of Cadmium on the Ultrastructure of Mice Sperm and Spermatogenic Cell and Gene Expression of bcl-2,bax in Male Mice

研究镉暴露对小鼠附睾精子和睾丸生精细胞超微结构的变化以及镉对生精细胞凋亡相关基因bcl-2、bax表达水平的影响。采用24只雄性ICR小鼠随机分为4组,每组6只,分别以0.183、0.915、1.83mg/kg氯化镉腹腔注射,每天1次,连续5次,设阴性对照生理盐水组。于第6天透射电镜观察附睾精子超微结构、睾丸生精细胞核和线粒体超微结构的变化,免疫组化方法检测生精细胞Bcl-2、Bax表达水平。透射电镜观察显示,0.183mg/kg组精子超微结构无显著性变化,0.915mg/kg组精子头部两侧膜与头部胞质间隙轻微扩大,线粒体嵴间腔扩大且轻度空泡化,但与对照组相比无统计学意义(P>0.05)。1.83mg/kg组头部两侧膜与胞质间隙扩大,与对照组相比有显著性差异(P<0.05),尾部线粒体嵴间腔扩大且轻度空泡化,与对照组相比有显著性差异(P<0.05)。3种剂量处理组睾丸生精细胞核超微结构异常发生率显著高于对照组(P<0.05),且随着处理浓度的升高异常发生率升高;1.83mg/kg组线粒体肿胀空泡化发生率显著高于对照组(P<0.05)。3种剂量实验组生精细胞Bcl-2表达水平(吸光度)显著低于对照组(P<0.01),0.915mg/kg组Bax表达水平显著高于对照组和0.183、1.83mg/kg组(P<0.01)。3种剂量实验组Bcl-2/Bax吸光度比值显著低于对照组(P<0.01);0.915mg/kg组Bcl-2/Bax比值显著低于1.83mg/kg组(P<0.01)。上述结果提示:高浓度镉诱导附睾精子超微结构改变,高中低浓度镉致睾丸生精细胞超微结构的改变,生精细胞超微结构发生凋亡现象。镉对Bcl-2、Bax表达水平的改变可能是生精细胞凋亡的分子机制之一。

The aim of the research is to study the effects of cadmium on the ultrastructure of mice sperm and spermatogenic cell and gene expression of bcl-2, bax in mice spermatogenic cell. Twenty-four male mice were divided into four groups. Three groups were treated with cadmium chloride by peritoneal injection using doses of 0.183 mg/kg, 0.915 mg/kg and 1.83 mg/kg respectively, once per day and five times in total. One normal control group were treated with saline. After exposure of cadmium chloride for five days, the ultrastructure change of mice sperm and the nucleus and mitochondrion of spermatogenic cell was observed by the transmission electron microscope. The expression level of Bcl-2, Bax in spermatogenic cell was assayed by the immunohistochemical method. The electron microscope observation showed that sperm ultrastructure of 0.183 mg/kg group was not seen abnormal plasma membrane and mitochondrion and for 0.915 mg/kg group there was a bit more distant from plasma membrane to cytoplasm with some big vacuolisations in enlarged mitochondrial intracristal space, but there was no significant differences compared with control group （P〉0.05）. There was significant differences （P〈0.05） between the 1.83 mg/kg group and control group for the sperm ultrastructure of plasma membrane and mitochondrial intracristal space. In three treated groups, the abnormal rate for the ultrastructure of spermatogenic cell nucleus is much higher than that of the control （P〈0.05）, more changes with concentrated cadmium. The rate of mitochon- drial vacuolization is much higher in 1.83 mg/kg group than that of the control （P〈0.05）. The expression level of Bcl-2 and the ratio of Bcl-2 toBax in three treated groups （0.183 mg/kg, 0.915 mg/kg, 1.83 mg/kg groups） were lower than that of control group （P〈0.01） respectively. The expression level of Bax of 0.915 mg/kg group was higher than that of control group and 1.83 mg/kg group （P〈0.01） respectively. The ratio of Bcl-2 to Bax in 0.915 mg/kg group was significantly lower than that in 1.83 mg/kg group （P〈0.01）. Taken together, we can propose that abnormal ultrastructure in sperm was induced by high dose cadmium. The abnormal ultrastructure and apoptosis in spermatogenic cell could be induced by low, middle or high dose cadmium. The change of expression level of Bcl- 2, Bax induced by cadmium would be one of the possible mechanism for apoptosis in spermatogenic cell.