MNU诱导视网膜变性大鼠bax和bcl-xl的表达及意义

目的检测bax和bcl-xl在N-甲基-N-亚硝脲（MNU）诱导的视网膜变性大鼠中的表达,并探讨其在光感受器细胞凋亡中的意义。方法采用Real-Time PCR法检测正常组和MNU腹腔注射后0.5、1、2、3、5 d大鼠视网膜中bax和bcl-xl的表达,TUNEL法检测各组大鼠视网膜细胞的凋亡。结果正常组视网膜中可检测到bax和bcl-xl的表达,MNU处理后0.5 d,bax表达上升,第1天达顶峰,第5天仍高于正常组;MNU处理后12 h,bcl-xl表达下降,第2天达低谷,第5天仍低于正常组。正常组未见TUNEL阳性细胞,MNU处理后12 h,外核层见少量TUNEL阳性细胞,MNU处理后第2天阳性细胞达顶峰,随后逐渐减少,第5天外核层仍有少量阳性细胞。结论bax和bcl-xl表达量的变化可能在MNU诱导的视网膜变性发病机制中起着重要作用。

Expression and significance of bcl-xl and bax mRNA in rats with MNU-induced retinal degeneration

Objective It is indicated that apoptosis of photoreceptors can be induced in rats by intraperitoneal injection of N-metbyl-N-nitrosourea（MNU）. Researches demonstrated that bax has a promoting effect and bcl-xl has the inhibitory effect on cellular apoptosis. Present study was to detect bcl-xl and bax mRNA expression in rats with retinal degeneration induced by MNU and discuss its significance in apoptosis of photoreceptor cells. Methods 40 mg/kg of MNU was intraperitoneally injected to establish the models of retinal degeneration in 30 50-day female SD rats. The animals were sacrificed and eyeballs were extracted in 12 hours,l day,2,3,5 days after MNU injection. Expression of bcl-xl mRNA and bax mRNA in normal control group and every model group were detected by Real-Time PCR. Simnhaneously, apoptosis was marked with TUNEL in all groups. Results Apoptosis of photoreceptor was found in 12 hours after injeetion of MNU. Apoptosis rate of photoreceptors was （ !9.2 ± 5.2 ） % , （36.8±6.8）%,（81.1±9.7）%,（51.9±8.4）%,（38.1±10.7）% in 12 hours,1 day,2,3,5 days after MNU injection. Bcl- xl mRNA was expressed in normal retina with the amount 25. 00×10^6. After MNU injection ,the bcl-xl mRNA level was gradually declined with the number 9.71× 10^6 , 8. 57×10^6 , 5. 44× 10^6 , 10. 39× 10^6 , 10. 93 × 10^6 in 12 hours, 1 day, 2,3,5 day respectively. Bax mRNA expression in retina could be detected in normal control group（4. 02 × 10^4） , and in the different time points above-mentioned ,the expression of bax mRNA in retina was 13.31×10^4 ,42.42 × 10^4 ,27. 17 × 10^4 , 10. 83 ×10^4 ,7.03×10^4 respectively. The bax/bcl-xl value was 1.00,8.52,30.78,31.06,6.48 and 4.00 in normal group,MNU 12 hours group,MNU 1 day group,MNU 2 days group,MNU 3 days group,MNU 4 days group,MNU 5 days group respectively. Conclusion Bcl-xl and bax may play an important role in the MNU-induced retinal degeneration.