Yasuo Shinobu, Yoshimura Takashi, Ebihara Shizufumi, Korf Horst-Werner
Dr. Senckenbergische Anatomie, Institute of Anatomy II, Johann Wolfgang Goethe-University Frankfurt, Theodor-Stern-kai 7, 60590 Frankfurt am Main, Germany.
Endocrinology. 2007 Sep;148(9):4385-92. doi: 10.1210/en.2007-0497. Epub 2007 May 31.
In many species living in temperate zones, reproduction is controlled by the photoperiod. Recent findings have clarified that type 2 iodothyronine deiodinase (Dio2) plays a significant role in the photoperiodic response of gonads in the mediobasal hypothalamus, converting the prohormone T(4) into bioactive T(3). In mammals, Dio2 expression is suppressed by long-term melatonin injections, although the signal transduction pathways that link the melatonin signal to Dio2 expression are unknown. As a first step to approach the problem, we have here investigated the temporal dynamics of the melatonin effect on Dio2 expression using male Syrian hamsters. Dio2 mRNA levels were found to show diurnal rhythms under long-day conditions in an area adjacent to the tuberoinfundibular sulcus and in the ependymal cell layer lining the ventrobasal walls of the third ventricle. Daily sc melatonin injections given in the late afternoon under long-day condition suppressed the Dio2 mRNA levels already at the first day after the onset of the treatment in the ependymal cell layer lining the ventrobasal walls of the third ventricle, and 1 d later in an area adjacent to the tuberoinfundibular sulcus. These suppressive effects were sustained for at least 2 d after a single injection. Furthermore, we examined the temporal changes of the Dio2 expression after the onset of the treatment, showing that the suppression did not occur until midday of the next day. These data suggest that melatonin is involved in the signal transduction mechanisms controlling the photoperiodic response of gonads by acting on Dio2 expression rather rapidly through indirect pathways.
在许多生活在温带地区的物种中，繁殖受光周期控制。最近的研究结果表明，2型碘甲状腺原氨酸脱碘酶（Dio2）在下丘脑中间基底部性腺的光周期反应中起重要作用，它将前体激素T（4）转化为生物活性T（3）。在哺乳动物中，长期注射褪黑素会抑制Dio2的表达，尽管将褪黑素信号与Dio2表达联系起来的信号转导途径尚不清楚。作为解决这个问题的第一步，我们在这里使用雄性叙利亚仓鼠研究了褪黑素对Dio2表达影响的时间动态。发现在长日照条件下，在漏斗结节沟附近区域和第三脑室腹侧基底壁内衬的室管膜细胞层中，Dio2 mRNA水平呈现昼夜节律。在长日照条件下，于下午晚些时候每天皮下注射褪黑素，在治疗开始后的第一天，就抑制了第三脑室腹侧基底壁内衬的室管膜细胞层中的Dio2 mRNA水平，1天后在漏斗结节沟附近区域也出现了抑制。单次注射后，这些抑制作用至少持续2天。此外，我们检查了治疗开始后Dio2表达的时间变化，结果表明抑制作用直到第二天中午才出现。这些数据表明，褪黑素通过间接途径相当迅速地作用于Dio2表达，从而参与了控制性腺光周期反应的信号转导机制。
