心肌肥厚大鼠心肌细胞核体外转录活性和RNA核孔转出的变化

Changes of transcription activity and RNA export of myocardial nuclei in vitro in pressure overload-induced rat hypertrophic heart

目的研究大鼠心肌细胞核体外转录活性、RNA核孔转出和核外Ca2+浓度([Ca2+])对其的影响,以探讨心肌重塑时核Ca2+在其中的作用和意义。方法制备腹主动脉缩窄大鼠心肌肥厚模型、差速离心和密度梯度离心提纯心肌细胞核,同位素掺入法分析心肌细胞核体外转录活性和RNA核孔转出。结果腹主动脉缩窄术后4周大鼠心肌显著肥大,伴有明显的血流动力学异常。与正常对照组比较,腹主动脉缩窄心肌肥厚组细胞核体外转录活性和RNA核孔转出明显增加。在核外[Ca2+]大于10-4mol/L时,转录活性和RNA核孔转出发生显著变化(P<0.05)。结论压力超负荷心肌肥厚发生时,细胞核体外转录活性上调,RNA核转出量增加,可能在介导基因表达异常中起重要作用。

Objective To investigate the transcription activity and RNA export of myocardial nuclei and the effect of Ca^2＋ on them in vitro in the development of pressure overload-induced cardiac hypertrophy. Methods The rat model of cardiac hypertrophy was established by abdominal aortic constriction. Differential centrifugation and isopyknic gradient centrifugation were employed to fractionate rat cardiac nuclei. The activity of nuclear transcription and the RNA export out of nuclei were measured by [ ^3H ]-UTP incorporation assay. Results Both transcription （RNA synthesis） and RNA export from nuclei in vitro increased in overload-induced cardiac hypertrophy as compared with those in control （P 〈 0.05 ）. The [ Ca^2＋ ] -response curves showed that transcription activity of myocardial nuclei in vitro kept at a plateau in the range of 0 - 10^-4 mol/L extra nuclear [ Ca^2＋ ], but were inhibited in more than 10^-4mol/L extra nuclear [ Ca^2＋ ]. Absolute exports of RNA were not significantly dependent on calcium concentration in both groups （ P 〉 0.05 ）, but relative exports of RNA were increased in more than 10^-4mol/L extra nuclear [ Ca^2＋ ]. Conclusion The transcription activity of nuclei and relative exports of RNA were regulated by extra nuclear calcium concentration （ more than 10^-4 mol/L）. The up-regulation of transcription activity and RNA export of nuclei might play an important role in development of overload-induced cardiac hypertrophy.