大鼠松果体Clock基因和芳烷脘N-乙酰基转移酶基因的昼夜节律性表达及光照影响

Circadian rhythms and light responses of clock gene and arylalkylamine N-acetyltransferase gene expressions in the pineal gland of rats

探讨12h光照、12h黑暗交替(12h-light:12h-darkcycle,LD)及持续黑暗(constantdarkness,DD)光制下松果体Clock基因和芳烷脘N-乙酰基转移酶基因(arylalkylamineN-acetyltransferasegene,NAT)是否存在昼夜节律性表达及其光反应变化。Sprague-Dawley大鼠在LD和DD光制下分别被饲养4周(n=36)和8周(n=36)后,在一昼夜内每隔4h采集一组松果体组织(n=6),提取总RNA,用竞争性定量RT-PCR测定不同昼夜时点样品中Clock及NAT基因的mRNA相对表达量,通过余弦法和ClockLab软件获取节律参数,并经振幅检验是否存在昼夜节律。结果如下:(1)在DD或LD光制下,松果体Clock和NAT基因mRNA的表达均呈现夜高昼低的节律性振荡(P<0.05)。(2)与DD光制下比较,LD光制下松果体Clock和NAT基因的表达振幅及峰值相的mRNA水平均降低(P<0.05)。(3)在DD或LD光制下,Clock和NAT基因之间显示相似的节律性表达(P>0.05)。结果表明,Clock和NAT基因在松果体中存在同步的内源性昼夜节律表达,光照作用可使其表达下调。

This study was to investigate the circadian rhythms and light responses of Clock gene and arylalkylamine N-acetyltransferase (NAT) gene expressions in the rat pineal gland under the 12 h-light: 12 h-dark cycle condition (LD) and constant darkness (DD). Sprague-Dawley rats housed under the light regime of LD (n=36) for 4 weeks and of DD (n=36) for 8 weeks were sampled for the pineal gland once a group (n=6) every 4 h in a circadian day. The total RNA was extracted from each sample and the semiquantitative reverse transcription polymerase chain reaction (RT-PCR) was used to determine the temporal changes in mRNA levels of Clock and NAT genes during different circadian times or zeitgeber times. The data were analysed by the cosine function software, Clock Lab software and the amplitude F test was used to reveal the circadian rhythm. The main results obtained are as follows. (1) In DD or LD condition, both of Clock and NAT genes mRNA levels in the pineal gland showed robust circadian oscillation (P < 0.05) with the peak at the subjective night or at night-time. (2) In comparison with DD regime, the amplitudes and the mRNA levels at peaks of Clock and NAT genes expressions in LD in the pineal gland were significantly reduced (P < 0.05). (3) In DD or LD condition, the circadian expressions of NAT gene were similar in pattern to those of Clock gene in the pineal gland (P > 0.05). These findings suggest that the expressions of Clock and NAT genes in the pineal gland not only show remarkably synchronous endogenous circadian rhythmic changes, but also response to the ambient light signal in a reduced manner.