Zn~(2+)对PTP开放和细胞色素c释放的浓度依赖性双向调节

研究Zn2+对Ca2+介导线粒体通透过渡孔道(PTP)开放和线粒体细胞色素c释放的影响,及其与线粒体膜电位(ΔΨm)和Ca2+介导的线粒体Ca2+释放(mCICR)之间的关系.提取大鼠肝线粒体,通过紫外分光光度仪检测不同浓度Zn2+作用下Ca2+介导的PTP开放状态;采用荧光分光光度仪测定不同浓度Zn2+作用下线粒体膜电位的变化;采用双波长双光束紫外分光光度仪检测不同浓度Zn2+作用下测试体系内Ca2+浓度的变化,以反映线粒体Ca2+的转运情况(即mCICR);通过免疫印迹法检测不同浓度Zn2+作用下Ca2+介导的线粒体细胞色素c的释放.高浓度Zn2+完全抑制Ca2+介导的PTP开放和细胞色素c释放.一定浓度的Zn2+部分抑制Ca2+介导的PTP开放和细胞色素c释放.适当浓度Zn2+自身介导PTP开放和细胞色素c释放.低浓度Zn2+加速Ca2+介导PTP开放和Ca2+释放;高浓度和一定浓度Zn2+分别完全或部分破坏ΔΨm;高浓度Zn2+完全抑制mCICR.当抑制mCICR时,Ca2+和Zn2+对PTP开放和细胞色素c释放的作用完全抑制.结果表明,Zn2+以浓度依赖方式双向调节PTP开放和细胞色素c释放.Zn2+的作用可能与Zn2+破坏ΔΨm和影响mCICR相关.

Bidirectional Regulation of Concentration-dependent Effect of Zn~(2+) on PTP Opening and Cytochrome c Release

Mitochondria are endowed with multiple Ca 2+ transport mechanisms by which they take up cytosolic Ca 2+ and in turn induces opening of permeability transition pores(PTP) and disrupts the mitochondria membrane potential(ΔΨm).The collapse of ΔΨm along with the release of cytochrome c from mitochondria is followed by activation caspases and apoptosis.However,the mechanism for the regulation of this system is poorly understood.The effect of Zn 2+ were examined on PTP opening and cytochrome c release mediated by Ca 2+ in mitochondria from rat hepacytein vitro. Results from UV spectrophotometer and Western blot revealed that the effect of Zn 2+ was biphasic:high dose was more 150 μmol/L Zn 2+ inhibit completely PTP opening mediated by Ca 2+ and cytochrome c release. As the doses decreased to 50～100 μmol/L Zn 2+ , the inhibition action was declined,whereas low dose of 0.2～0.5 μmol/L Zn 2+ accelerated the PTP opening and cytochrome c release. Both high and low doses of Zn 2+ could completely or partially destroy mitochondrial membrane potential measured by fluorescence spectrophotometry.The dual_directional regulation observed for PTP opening and cytochrome c release by Zn 2+ was concentration dependent,and might be involved in the collapse of mitochondrial membrane potential and Ca 2+ _induced Ca 2+ release from mitochondria.