摘要
研究核外Ca^(2+)浓度对核Ca^(2+)的影响,及细胞核Ca^(2+)摄取和释放的关系,以探讨核Ca^(2+)转运的调节机制。采用差速离心和密度梯度离心法分离纯化心肌细胞核,以Fluo-4/AM荧光指示剂负载心肌细胞核,应用激光共聚焦扫描显微镜和荧光分光光度计进行观察和测定。结果显示,分离纯化的成年大鼠心肌细胞核内自由[Ca^(2+)]随着核外[Ca^(2+)]的增加而逐渐增加,孵育液[Ca^(2+)]为1000 nmol/L达高峰,但二者增加的程度并不一致,之后随核外[Ca^(2+)]浓度的增加而呈降低趋势。ATP和100—600nmol/L的核外游离Ca^(2+),使心肌细胞核显示核被膜腔Ca^(2+)荧光,ATP和1000nmol/L的核外游离Ca^(2+)则进一步引起核浆内的Ca^(2+)荧光强度升高。荧光染色观察可见IP_3受体染色主要位于核内膜,而钙泵和ryanodine受体染色主要位于核外膜。IP_3和Ryancodine使核Ca^(2+)短暂升高1.68倍和1.93倍(P<0.001),而钙泵抑制剂Thapsigargin和IP_3受体抑制剂Heparin则分别使核Ca^(2+)降低64%和35.6%(p<0.05)。ryanodine使IP_3升高的核Ca^(2+)显著回落至正常水平以下(p<0.001)。Thapsigargin不能阻断IP_3和Ryanodine所致的核Ca^(2+)释放增加(p<0.05),但事先采用钙泵抑制剂Thapsigargin预处理心肌细胞核,则能显著的阻断IP_3和Ryanodine所致的核Ca^(2+)升高作用(Ca^(2+)释放作用)(p<0.05)。结果提示大鼠心肌细胞核可能也是细胞内的钙库之一,心肌细胞核上存在Ca^(2+)-ATPase、ryanodine受体和IP_3受体等Ca^(2+)转运系统,可能参与核Ca^(2+)摄取和释放的调节。
To investigate the regulation of Ca2+ in the isolated cardiac nuclei from rats which may illuminated the mechanism of nuclear calcium transport system. Elocity and isopyknic gradient centrifugation were employed to fractionate rat cardiac nuclei. Then fluo-4 confocal microscopy techniques was used to verify the changes of nuclear Ca2+ . There are calcium-dependent Ca2+ uptake in the cardiac nuclear obtained from normal rats, The accumulation Ca2 + of cardiac nuclei in vitro from the incubating medium were not consistent with free [Ca2 + ] in incubating medium. The nuclear envelope was initially loaded with Ca + (1 mmol/L ATP and approximately 100 nmol/L Ca2+ ), Adequate Ca2+ loading was next confirmed by imaging the nuclear envelope and nucleoplasm. Exposure of Ca2 +-loaded nuclei to IP3, ryanodine or ryanodine+ thapsigargin, respectively, resulted in a rapid and transient elevation of nucleoplasmic Ca 2+ free concentration, this effects were abolished by pretreatment of cardiac nuclei with Ca2+ -ATPase inhibitor thapsigargin. Thapsigargin and IP3 receptor antagonist heparin induced nucleoplasmic Ca 2+ free concentration decrease. Fluorescence experiments indicated that both ryanodine receptors and Ca2+ -ATPase were distributed in the outer layer of nuclear envelope, and in-ositol 1,4,5-trisphosphate receptors mainly dispersively localized at inner layer of nuclear envelope. The present study demonstrates that nuclear calcium were regulated by free Ca2+ , IP3 and ryanodine, The results suggested calcium transport system might be present in the myocardial nuclei, the myocardial nuclei might served as one of calcium pools in myocardial cell.
出处
《实验生物学报》
CSCD
北大核心
2002年第2期127-134,共8页
Acta Biologiae Experimentalis Sinica
基金
国家自然科学基金资助课题(No.39870347
No.39870392)